Your dog might be happier inside the tent, protected from bugs and snuggled against you for warmth. (I consider my dog part of my sleep system!) That's especially true if your dog is crate-trained. My dog considers my tent as _his_ personal crate (note the pronoun!). He sleeps happily through the night with little disturbance, which is definitely not the case when we're under a tarp (I tried the latter and he was awake and restless half the night!). Of course your dog may vary!
I keep my dog's claws trimmed short and have had no problems with silnylon or cuben tent floors. I do move my WM sleeping bag and insulated air pad out of his way when taking him in and out of the tent! He sleeps either at my side or at my feet, so I can get in and out of the tent during the night without tripping over him. If he were in the vestibule, I'd be falling over him every time!
I also comb my perpetually-shedding dog at bedtime every night. It makes him feel good, means less dog hair in the tent and removes any ticks that might be crawling around on his fur.
If you're going to put your dog in the vestibule, you really should have a tent with two doors and two vestibules, so you can have the dog in one and your shoes (especially if muddy) in the other, and you can go in and out without disturbing or tripping over him.
Do note that cramming a dog and a human into a solo tent will probably overwhelm the ventilation system and result in more condensation than you want inside! (Been there, done that!) I'd look for a 1.5 or 2 person tent. Note also that closing the vestibule for the dog, if he sleeps there, will also cut down on ventilation and therefore increase internal condensation.