We had the folding one, but it's pretty bulky for camping use.
I also had one of the aluminum folding ones that went in my trailer hitch. I liked it but my lab didn't.
Some dogs are okay with ramps but not steps and vice versa. There are tons out there if you go to the pet supply sites. Try http://www.discountramps.com/pet-products-page.htm;
they've got about every ramp and/or steps for every animal from hamsters to elephants. My dog can't travel anymore, but if he did I'd be looking for something that could be put to other uses, always a plus in our vans. Some folks also have room in the back to put in a sliding ramp that slips up under the van body; dunno if yours does that but it's a nice solution.