It'd be significantly heavier. And significantly thicker if you use a case too.

Im actually fine with that. The leather apple case doesn't add too much weight as it is but I feel the phone is way too light and slippery without it.

I've been using the same leather Apple case for 2 years (6/6S) and it looks like crap at this point, but it's protected my phone from numerous 3-6' drops onto hard surfaces. Without the case, I'm certain the corners would be dented and the screen likely cracked. Definitely a fan of the Apple case!

I agree — I think it's a bit of a trick to compel people to feel the need for a case, thereby selling more cases than if it were flush.