I'm lucky enough to have both the KTM 790R and Yamaha 700 Tenere. I can ride them back to back and compare them long-term.
I can't do a well-rounded comparison. I don't do nearly as much "ADV" riding as I'd like to. It's been almost 2 years since I loaded up with camping gear and was out on a backcountry overnighter or even rode on the highway for more than an hour. I'll tell you what I can though. They're different tools for different jobs. Riders need to be honest about what their needs really are. Everyone wants to ride like Chris Birch but how many people will be able to regardless of what bike they are on? 1%? 0.5%? Less?
Hard Fast Riding:
The 790R excels at going fast. It destroys the T7 in rough, open terrain. The 790R suspension is simply better. It's not very plush but when you really start pushing the bike, it starts to work really well. The T7 suspension can't compete and honestly, how could it? You have 790R with 240mm travel and 48mm forks with 25mm cartridges vs the T7 with 200mm travel and 43mm forks with 20mm cartridges. Even with a respring/revalve, the shorter stroke and smaller cartridges/pistons in the T7 forks will be the limiting factor. Even with a respring/revalve from a great tuner, I doubt you'd be able to get the T7 suspension even close to the level of the stock 790R. The T7 will work well for spirited rides for most people as long as you're not too heavy and the terrain isn't too rough. Riders who usually just buy a bike and ride it with totally stock suspension will be happy with the suspension of the stock T7 too. If you're the kind of rider that gets all or most of their bikes revalved/resprung, this one will be no different.
Slow Technical Riding:
For slow technical riding, I'll jump on the T7 over the 790R every time. The T7 is an f'n tractor, it's a gorilla, it just chugs along. The low-end torque this thing has is incredible. It is very confidence-inspiring off-road. This CP2 motor is perfect for this bike and the gearing is on point. The 790 has good mid-range and top-end power but the bottom end is lacking and it's geared tall. It requires a lot more clutching to ride the same technical terrain. I went down one tooth on the front and up 3 on the back of my 790 and now it's slightly more stall resistant than the T7... that's a huge gearing change. If you don't spend much time on the highway, then gearing the 790 will make a huge difference in its usability for technical. The T7 just works out of the crate.
790: I feel really cramped on the 790. The footpegs are quite far back so my feet are under my ass, feels sportbike like. The peg location is great once you're standing as you're a bit more stretched out and stable but for sitting, they are too far back. The sitting to standing transition is less than ideal. Even with the KTM PowerParts tall seat, moving up and down wrecks my knees over the course of a couple hours. The bars will feel low for most people. Over the past few years, my preferred bar height has come down a lot. I started with 4" bar risers on my first ADV bike and as I get better offroad, my bars have started coming down. The 790 bar position feels pretty good for me as is. The stock standing position works well for hard and fast offroad.
T7: The sitting position is excellent and comfortable for long days. The pegs are a few inches forward so I'm not nearly as cramped sitting. The bars are very tall, most people that have sat on my bike have assumed I've added risers. This creates a bit of an issue for me when standing as I don't have the same "base" as I do on the 790. I need to lower the bars a bit to find the sweet spot. The sitting standing transition is much better than the 790 for me YMMV. The forward location of the footpegs and tall bars means I'm standing taller and having to hold on to the bars harder which puts more strain on my shoulders, back and forearms. This bike is begging for Stegz Pegz. If you don't know what they are, Google them. They've been a game-changer for me offroad (on Japanese bikes anyway).
The T7 doesn't have traction control but I don't think it needs it... it makes good tractable power and doesn't seem to want to spin wildly. I do wish it had Offroad ABS though. I thought it was gimmicky when it came out a few years ago but I have grown to like it, a lot. I also wish the T7 would retain the ABS setting when you turn the key off and back on. It's annoying (and dangerous) when the ABS defaults back to ON when you're doing sketchy offroad riding, grab the brakes and get basically nothing as you are headed toward <insert something you don't want to hit, or ride off of>.
The TFT display on the 790 beats the T7's Gameboy looking unit. That been said, my TFT was replaced under warranty for condensation in it after 1000km... and is leaking again so perhaps a waterproof Game Boy beats a leaking state-of-the-art TFT...
Wheels: I run tubes in everything I own so the 790R's tubeless isn't an asset to me. YMMV.
Wind protection: A draw, they are both m'eh for me @6'3"
The 790 carries 25% fuel more and the range seems to reflect that too.
The gas gauges suck on both of them. The 790 doesn't start to read until a 1/2 tank. That's not an issue with mine, literally, the gauge starts at 1/2 and goes from there. I assume this is because of the tank's very weird shape. It would be very difficult to get a float/sending unit to work with the shape. Even though you know the gauge starts at half (meaning the gauge showing 1/2 tank is actually 1/4), I'm, still adjusting to it... have run out of fuel twice.
The T7 has a full gauge but it's not very accurate. When it reads empty, mine still has 3/8 of a tank left, not helpful.... and, I don't want it to read full longer, you're not conning me into thinking the bike is way more efficient than it actually is! I wish someone would just build a gauge/float that was accurate. Full means full, half means half and empty means you're pushing. At least that way I can plan accordingly.
You'd think the T7 would feel much more top-heavy with the fuel all up top compared to the 790 being very low... somehow, it isn't that noticeable. I have a few ideas about how to actually measure it... that will be interesting to see that actual results.
For BDR type rides, either will work but I'd be more comfortable on the T7... it's just an easier bike to ride. The 790R is a more race-type bike and needs to be ridden hard and fast to be truly appreciated. If I am going riding in the desert in Southern California or Nevada, I'll take the 790R. However, after I swap to top-shelf suspension on the T7, this will be closer to a draw.
If I'm riding nasty technical trails at home (that I really should be using my actual dirt bike for), the T7 would be my pick. But... after really gearing the 790R down and this gets closer too.
Yamaha will sell a PILE of T7s. I think it's the new KLR... I don't mean that in a negative way. It's an inexpensive bike that should be reliable (I haven't had any issues and I'm not seeing many online yet). It's a great beginner bike (my noob girlfriend has a deposit on one) but it appeals to experienced riders too. There's no new tech in it, just tried, tested and true parts.
They are both great bikes but definitely have different target audiences (with a bunch of cross-over).