What's your price range. A lot of what are considered key features are built into more high end smokers but lacking on lower end ones.
Do a search for offset smoker mods and see what people are doing. That will give you good idea of what to look for as features.
The thicker the wall of pipe, the better too. Like you said, a deflecter plate & charcoal basket are 2 to look for. I wouldn't be stuck on 2 thermometers because if you have a deflecter the tmerature gradient should be near 0. Make sure it rolls nice and easy if you plan for it to move. My smoker needed a mod to make it roll easier.
Ease of airflow adjustment is another. Make sure to have a big flat area to prep on and ease of cleanup of the surface.
Really want to stay below $400...and am willing to complete the mods myself...does a deflector mod really need to be installed/welded in...couldn;t a less afficient design be used to achieve similar results...ex. aluminum foil?
I don't think aluminum foil would work long term. It needs to be fairly rigid with holes in it to disperse the heat throughout the cooking chamber. I think foil would fail quicly. If you look around SMF you'll find pics of deflector so you can get an idea of their design. Once you get a smoker, make up a cardboard template inside the smoker. Hit up a buddy or small business to make one for you. Offer some smoked deliciousness to them and you might score it for free.
Buford, welcome to the forum. Glad you are looking for a Smoker. There are lots of things you would (cost prohibited) want , check out the Signatures on the bottom of a lot of the Member's post.
I for one would want a solid Smoker , decent heavier Smokers can be over $400. You can get a Horizon for about $600. at the Bass Pro shops, and they would last till you pass them on in your Will (if you take care with them).
The Mods. are not necessary if you don't want them and learn your Smoker without them , however efficiency is your goal.
Look for grill space , design ( do you want a big one or want a wood burner ,Elec. Gas , etc.) and definitely get some good Thermometers . Then set about learning your Smoker ; how it heats , the hot spots , quality of your Cooks ( comes with practice) and ease of operation.(ex. - see my profile pics).
First off you need something to contain the smoke, a fuel source, dampers for controlling air flow, racks for holding meat. finally a way to move the meat into and out of the smoker, that's basically it. A thermometer would help too.
The biggest issue in a smoker it uneven heating, one side gets hotter than the other in a side by side, or the top gets hotter than the bottom in a vertical smoker. leakage is probably the second issue, no use smoking if all the smoke if exiting from the wrong place.
I think your first decision needs to be fuel source, from there you can limit your selection.
For a new to smoking smoker at the $400 price point get a 22.5" Weber Smokey Mountain. It works right out of the box with absolutely no mods, has a small deck foot print while still holding a ton of meat, and is as close to set-it-and-forget-it as you cane get with a charcoal/wood smoker. I started with a very frustrating cheap(ish) $200 horizontal offset, spent $$ on mods, got OK results, then sold it on Craigslist for $80 - bought a 22.5" WSM and have never once regreted it.
.... and to give you an idea of how much you can fit - I just did 45 lbs. of pork butts and 45 lbs. of brisket at the SAME TIME for a BBQ for my folks! It was a tight squeeze, but it all fit!
Follow Rodriguez's advise and I'll guarantee you will be happy. I was scanning the responses to your question and formulating a reply in my mind. Then I read the comment about the Weber Smokey Mountain and knew that I couldn't improve on it. That's exactly what I did. I moved from the el cheapo to the $ 200 horizontal. I did the mods and had fair results. But I then moved to the WSM and like Rodriguez, I have never looked back. For the money, it just can't be beat. It has great capacity, you can almost set it and forget it and it comes ready to go right out of the box. As a matter of fact, I have even seen them used in competition.