I thought about going with a 6.5 Grendel two years ago for deer hunting in our woods. Ballistics were pretty decent at reasonable ranges, but it struck me as a long range "plinking" round for guys that wanted to shoot long range without the recoil. Then I compared it to the new 350 Legend and ended up going that route for a few reasons:
1. Energy. Not retained energy, but rather energy transfer. The 350 Legend shoots a heavier, larger diameter bullet that will transfer more energy to the target (deer). We only have 28.5 acres, so my shots are usually well inside 150 yards. The larger bullet not only dumps more energy, but also produces better blood trails due to the larger entrance wound. I blood trailed a lot of deer shot with a .243 Win...if you didn't get an exit hole, have fun tracking!
2. Ammo availability. Both cartridges are new, but the 350 Legend was designed and heavily advertised in the deer hunting community. Wisconsin is not a straight wall state and most guys will not opt for a 350 Legend over a bottle neck cartridge like a .243, .270, .30-06, 7mm, etc. Almost every store I have gone into the past 2 years has had 350 Legend ammo. I have only seen 6.5 Grendel ammo a couple times and it was steel case FMJ, which is not legal for hunting here, and even so it was considerably more expensive than 350 Legend ammo.
3. Recoil / Shootability. I have two kids. The low recoil of both the 6.5 Grendel and 350 Legend are appealing for young or small-statured shooters, but the forgiveness the 150 or 180 grain projectile offers a novice shooter tips me in favor of that cartridge. An amped-up kid shooting their first deer at 75-100 yards may miss by a few inches and shoot into a shoulder...that 150 or 180 grain bullet at 2100-2300 fps will hold up against a leg bone or shoulder much better than a 120-ish grain bullet travelling a few hundred fps faster.
4. Barrel length / Ballistics. As mentioned already, the 6.5 Grendel was designed around 22-24" barrels. Whack 6" off that barrel (think AR platform) and you will lose a LOT of velocity (an energy) as a result. The 350 Legend was designed around shorter barrels and has very little velocity change in longer vs. shorter barrels.
I know you said you were not looking for recommendations, but for others reading this now and in the future, I shared my decision making process more for educational purposes than recommending a caliber. In my opinion there are better deer calibers than the 6.5 Grendel for whitetails, especially in the Midwest. I think a 123 gr. SST in a 6.5 Grendel would make a FANTASTIC coyote round at 2500ish fps. At the end of the day, I think the 6.5 Grendel was developed as a long-range target shooting round which could be loaded with hunting bullets and the 350 Legend was developed specifically for hunting Midwestern whitetails, which it seems to do very well! I originally bought an 18" AR upper in 350 Legend, but liked the round so much, I added a bolt action to my collection as well.
ETA: I should also mention I was not worried about the 200+ yard ballistics (or lack thereof) of the 350 Legend, as I also have a .243 Win, .270 Win and .30-06 SPRG for longer range hunting.