One option to consider as well if you're worried about ending up with unfamiliar gear is to rent from your "home" shop and take it with you. Downside is that you have to schlep gear all the way there and back, and pay for the rental for the entire time you're away, but upside is that you will be able to use stuff that you are already familiar with. Even if you hit a different shop to try out a new type or brand, you might still be able to arrange some pool time with it before hand so your first experiece with those pieces aren't when you're making a giant stride off the back of a boat.
I agree with Pelagicsal though, on diving more if you have your own gear -- especially if you have local diving options available. It becomes a lot easier to head out when you're not shelling out $50-100 in rental gear each time, then having to make it back in on Monday to return everything. We are fortunate to have a local mud-hole to go get wet in, but we usually don't decide to go out until the night before or day-of. As long as the tanks are full, the only detour we usually have to make is to get cash for our entry fees. If we had to rent, the dives just wouldn't happen nearly as often, both for cost and convenience.
On the other hand, if decide that local diving is simply not in the cards for you, and you're only going to make one or two trips a year (or less!) then you might want to consider just renting when you need it. A lot of dive gear takes as much "wear and tear" from sitting around as it does from being used. The pristine gear that gets used once a year on vacation may actually be in worse condition then the stuff that gets used every weekend and never really dries out.
As mentioned above, some things make sense more than others to own. A wetsuit is very much dependent on fitting right to work effectively. Even IF you happen to be a relatively "standard" size body, different brands and models will fit the same person differently. At the same time, it's water temp dependent so make sure you take into consideration where you're going to use it. Having a 7mm suit suitable for local quarry diving isn't going to be much fun when you're jumping into 82 degree tropical waters. Then there's the Pee factor
Regs are pretty much regs. The big X-factor with rent vs buy is how they're maintained. A good rental shop will have newer, well maintained gear. This is precisely one of those pieces though where not being used can be worse than daily use. If you own, or rent locally before a trip you have the option to try things out in a controlled environment. On the other hand, even the best prepared gear sometimes develops issues. If it's rented on-site, the shop can probably fix it or quickly swap it out. If it's yours or a home-rental, they may or not be able to help. Backup plan there is to rent theirs. The "Ewwww" factor with regs is going to be that it's something gets stuffed into your mouth. Nothing a little listerine can't fix (or hide), and you might consider bringing your own mouthpiece (and zip ties) if you're really worried.
The BC doesn't have the Ewww factors so much, but again, you have to factor in maintenance and care. External condition is easy enough to assess (straps, obvious tears) but a small leak may not get discovered during the normal rental turn-around process (i.e. hang it up to dry). The power inflator, like the regs, has seals and o-rings that like to be used, not sit around. Like your exposure protection, fit is a factor, just just about all BC's have enough adjustments to get them close enough to be comfortable, effective, and safe. Where the BCD differs though is in familarity. Different makes/models put things in different places. Air dumps may be in different places that you can't really see while wearing so knowing how to find them by touch is good. Weight pockets (if you use them) may function differently. How you arrange your weights can change - the same weights spread out into different pockets (and/or on a belt) will affect your "trim" or posture in the water. Not show stoppers, but things that you might take a few or more dives to try different things and get comfortable with.
There's no single right answer to the question, just things to consider when making your own decision. Get in the water and see what things you like or don't like and go from there. Talk to your shop owner and see what kind of options they have - they may have a rent-to-own program that lets you credit your rentals towards purchasing your own gear. Get thru the class though before making any big investments - you may find that when you hit the open water that diving isn't for you. Or, like most of the dive junkies on here you end up spenind every waking moment figuring our how you can get more bottom time
