Follow this link and it should take you to the Bobcat web page, where you can select the model and year you're looking at and it'll bring up the spec sheet for that model.
http://www.bobcat.com/products/historical/lookup.html?machineType=SSL
If the link doesn't work, go to the Bobcat home page and select "products" then the fourth from the bottom of the drop down, select "historical data" and you'll get to the same place.
In the 700 c,f and k series the 753 is the same catagory as the S130 which has a lift capacity of 1300 lbs and is a radial lift. The 763 is also a radial lift and is the same as the S150 with a 1500 lbs capacity and a longer wheel base and higher lift than the 753. The 773 is a vertical lift machine, same wheel base as the 763 but a little more lift height and is rated the same as an S175 at 1750 lbs, but in the last few years (K series) could be had with a turbo option, air conditioning, and a slightly higher capacity rated at 1850 lbs which matches the S185 available new today.
Last year when I was in the same boat you're in, I weighed out what I wanted against what I felt I needed and came up with a 1997 763 with cab and heat. A 753 will load most tandem dump trucks, but barely. The 763 has better lift hight and clears the side boards better, but I wouldn't want to do this alot. Now the 773 clears the boards nicely, and being vertical lift the bucket is farther out from the cab and hits the center of the truck better, which saves having to load both sides of the truck to keep the load balanced. But, it has way more pins to get sloppy and visibility isn't near as good out the sides. It was the 773 I wanted, but the simplicity and extra capacity of the 763 that I decided I needed. It seems there are many more attachments available to the 763's and above than there are to the 753's, it's almost like a dividing line between big and small. I also found the 753's and 763's to be very close in price used, but the 773's were 2-3,000 more with similar hours.
Hope this is of some help to you, and good luck on the search for what fits your needs best. I'm currently on the hunt for a used dump truck, and hopefully can report back with positive progress in the next week or so. Dang, I love buyin toys, but I could live with-out the stress of making sure I'm getting the right ones to fit my current needs as well as the fore-see-able future with-out breaking that always fragile bank.
Don