Wetsuit advice

There is no point in getting neoprene shorts/pants for a race. Those really don't offer much warmth, just some extra buoyancy. To my knowledge, they are mainly used as a "training aid" (AKA crutch in many cases), mostly by triathletes with poor swim skills and buoyancy issues. At any rate, they are generally not permitted in a race that is not wetsuit legal. July races are iffy--in many places it's uncertain year to year if water temps will make the race wetsuit legal or not (wetsuits are generally not allowed below a cutoff temperature). Definitely make sure you are not depending on your suit to complete the swim.

Whether you would rather get a sleeveless or full suit would be a matter of expected water temperatures, swim skill, and personal preference. Suits with sleeves are of course a bit warmer and offer more buoyancy. For colder water or weaker swimmers, I would recommend a full suit. A full suit will also keep you warmer before the start if you will be standing around pre-race when morning temps are quite low (such as at some events in the Pacific Northwest, Canada, or high altitude races).

If you are a strong swimmer who just needs the suit for warmth, not buoyancy, and temps are expected to be marginally wetsuit legal, then you could go with sleeveless if that feels more comfortable to you. Some people feel like they have a better range of motion and are more comfortable in the sleeveless.

I personally have both. (My sleeveless is an unusual shortie length one.) I'm a pretty strong swimmer for my age group, but kind of a cold-water wimp. I generally wear the full suit until water tops about 71 or 72 degrees F. For anything warmer up to the cutoff temp, I wear the sleeveless, unless pre-race air temps are really low. That being said, I have done short swims with the sleeveless down to 62 degrees and lived to tell about it; certainly even at colder water races (like Coeur de'Alene or Calgary), you do see some athletes (usually confident swimmers carrying more muscle and body fat than me) in sleeveless models.

I would go full wetsuit or nothing unless you're thinking the race is right on the wetsuit legal temp line and are worried about the heat. But I've swam in pretty warm water in a full suit and it hasn't been bad. I've never had chafing issues (aside from the back of the neck, but that'd be an issue with regardless of sleeves).
My Zoot is the only suit I've ever had and it still works great 5 or 6 years in. I think it was about $300.

I see that xterra suits have a green suit called 'vivid' on sale for $119 .... thin neoprene on the arms ...

I had the same experience. My first full suit was a cheaper entry-level model, and I felt like it wore out my shoulders and restricted my stroke. I have a small build and probably lacked the muscle to push against the stiffer, thicker neoprene. Maybe not an issue for bigger, stronger people? Or could have just been a fit problem.

I replaced the full suit a few years later with a higher-end model that I found on closeout. (All my suits except the first, a TYR, are from an Oregon company called ProMotion.) Like many such suits, it has thinner neoprene in the arms and some kind of panels to improve mobility. No issues with comfort or mobility in that one--I can swim as easily as in the sleeveless, or without a wetsuit. It seems like with the full suits, you get what you pay for in terms of better materials and design. A cheaper suit will keep you warm and provide plenty of buoyancy (sometimes more than the higher-end models, which are often marketed toward faster swimmers), but you'll probably get a bit less mobility and comfort.
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What I like best about their suits is that many models have calf zippers. I'm medium tall and skinny, and for fit purposes usually end up in a suit intended for somewhat shorter women. Many models' "ankles" fall at mid-calf on me and with muscular runner's calves, that is next to impossible to get out of without a zipper. Saves a ton of transition time and pre-race greasing up!