Here is what I would look for......If you already smoke with wood or charcoal than you probably want a gas grill for the speed and convenience of not having to wait to cook, so.......I am narrowing your options some.
Get atleast 3 burners so that you can have 3 zones, preferably left to right so that you can turn the middle one off if you are doing a roast with a drip pan. When grilling, you will be able to easily set up 3 zones at high, medium, and low for moving your food around as needed. Might as well get a good side burner too:-)
If you go for a stainless steel grill, try to get one that has a double wall hood. Also, the hood should be all welded rather than screwed together.
Make sure the
grill grates are either cast iron or solid (not hollow) stainless steel rod, something atleast 1/4 inch round.
Try to get thick cast burners that will last and be able to stay intact because of the high heat.
The drip bars above the burners also help spread the heat evenly, so check out the thickness and design of these bars. In the old days, they used lava rocks for this. I like the racks with ceramic tiles which seem to spread out the heat some, but they do crack over time.
Look over the burner area to see if it will be easy to take apart in the future for cleaning, etc. Look for a removable grease pan or drain area.
I am sure I forgot something, but Good Luck:-)
Steve