Ah, the M7 .... personal fave these days.
We've one in both calibers you mentioned - The Wife's 7-08 & my .308 - both sweet.
Lightweight, very handy - both in standard off-the-shelf condition except for the free-float, glass-bed & trigger jobs (+ 1-piece scope mount & optics).
As mentioned, no deer will know the difference (but I've had "an experience" with a deer once with the .308 ... )
However, using the 18.5" bbl, you may be disappointed with the velocities if you're used to more "blazing" rifles.
We're getting right at 2600 fps with Nosler Ballistic Tips 120 gr in the 7-08 & 2400 fps with Barnes XBT 165 gr in the .308 (IMR 4064 & IMR (mumble - 4150 ?) in the .308) - you may be able to boost 'em up with some decent load development. Both do kill cleanly, but the trajectories could be improved upon with what we're using. To 200 yds, these velocites just don't matter at all.
The "7" though, has a standard deviation of 6 (yup) for 10-shot groups & is a tack-driver. .308's not too far behind but no bragger - yet.
Haven't tried any 110s or 130s in the .308 (which should get velocities up around 3K fps) yet (same for the 7 but can't really comment about bullet weight availability - it's a "newbie" still for me). On the list ... but should reach out there pretty good & esp w/130s, drop the lighter deer right there. Understand, the .308's just been used (mostly) for elk - deer loadings have taken a second seat.
If you will ONLY shoot deer up to the 150 lb class, I'd go for the 7, but if you ever had the inclination to go for bigger game, I'd get the .308 ... well, heck, I'd just go for the .308 & be done with it.
7mm is supposed to be "that one optimum caliber" that will do it all oh so well. Can't disagree, except for all the selection available for the .30 cals. Still waiting on the "report from the field" on the Barnes XBT 140 gr (~2400 fps) on elk - hopefully a report forthcoming in about 6 weeks.
Everything in the world has been killed with one shot out of a 170-200 gr bullet moseying along at 2100 fps .... both The Seven & any .30 cal will do that.
The .30 does allow a bit heavier bullet AND there is the availability of a wider factory selection ....
YMMV ...
... actually, probably should have just gotten a .308 for The Wife ...