The biggest difference between a Timeshare Rental and Vacation Home Rental is from the owners point of view. As a timeshare owner, I own a 1/52 interest in a specific unit at a specific resort. I pay a maintenance fee to a management company to maintain the unit, provide housekeeping, security, and common amenities. A Vacation Home has a single owner for the entire property who (usually) pays a management company to look after renting the unit and maintenance, and pays condo or association fees for any common elements and security.
From the renters view, with timeshare resorts the developer/management company often holds a stock of unsold inventory that they are allowed to rent to the general public. Many (like Sheraton) run this like a hotel operation. If you rent from Sheraton directly for Vistana for example, you can get daily housekeeping and free shuttles (or pay less for the standard mid-week housekeeping/towel refresh) which makes it very close to a hotel stay, but with a lot more space, bathrooms, cooking and laundry facilities than you will find in a suite hotel.
One thing though is to watch the fine print on very cheap "special packages" from a developer; they may require a timeshare presentation. Not that that is a necessarily a bad thing; if you are willing to give up a half day of your vacation for a really good rate, you can consider it, but steel yourself for the presentation. Just don't EVER hand over any money, and remember that if the salesman's lips are moving, he/she is lying. All timeshares are available for considerably less than developer cost in the resale market; and there is no real difference between new and used - this is not like a car; even their "new" units are pre-enjoyed by others...
There are ways to rent timeshares directly from owners as well; check classifieds at
http://www.tug2.net/ or
http://www.redweek.com/ for a good source of owner timeshare rentals. These are usually (but not always) less expensive than direct from the developer. Owners usually are happy to recover their annual maintenance fees (generally $800-$1000 per week for a nice resort), so $100-$150 a night is normal. If it's less than $100, the owner is probably in a net negative situation, so be nice Note that owners do generally get pretty mad at our management companies when they start renting for less than we pay in MF's.
Vacation homes in the Orlando area are often in gated communities like Windsor Hills that were purpose build for the vacation industry. They have a lot of amenities but (arguably) not as many as good resort, and usually have the advantage of a private pool. There are a lot more sizes available too, TS resorts generally top out a 3BR, but there 7+ bedroom homes available if you need that much space. A couple of negatives that I have heard; many charge extra if you want to heat the pool, and many require you to do a bit of your own housework, expecting the renter to do a certain amount of housekeeping themselves on departure.
So between the two it really comes down to a balance of how much freedom you want, how many amenities you want, how much space you want, and what you want to pay for it all.
However, it was 2010; right after that unusually cold winter where birds were falling out of the trees and whatnot. 
The kids did go swimming in the big pool and enjoyed the slide and all, but middle daughter thought it was way too cold as did hubby, so it was only the one time. The boys didn't seem to mind the cold but we were in the older buildings so much closer to the indoor/outdoor pool anyhow. Every time we went by the big pool there were a few people happily swimming in it, but most people were sticking with the heated one. 
Anyhow, I would guess in a "normal" year, the big pool in early May would be fine for people who don't mind unheated pools in general. If it's been cold recently, not so much.Our kids had a 4 day weekend that Sept for Jewish holidays so we couldn't stay the full 7 nts but even 4 or 5 nts it's still a bargain.
and almost stepped on them. Luckily he did a quick leap over the whole stroller and kept going but nothing resembling an apology or even an "oops, excuse me". Just a lot of minor annoyancess that kids probably wouldn't be doing if their parents were there. (spitting, cursing, etc.)
Now that my kids are past the elementary school age, they can't miss a week of school without major damage so that week is out for us.
Note that owners do generally get pretty mad at our management companies when they start renting for less than we pay in MF's.
