As some one mentioned earlier, they are long, so when they get older you have to be more careful with them to prevent back problems. For Telly, anything under 2'-6" is fair game, floor board of my jacked up truck, back of the Explorer, on top the bed (bad dog), into the trailer in a single bound, etc..... He is a good judge of what he can and can't do, on some of our more rugged hikes he'll wait patiently for me to either put him on top of the next ledge or lift him down to the next ledge (you have to be paying attention because he'll jump into your arms before you are expecting it so he can move on to the next interesting thing to investigate). He needs brushed once a week, all the swimming he does helps a lot in the summer.
IF you don't mind all the shedding, and IF you are willing to do basic obedience training and lay down the law, and IF you want an intensely affectionate and loyal dog that will love you to the ends of the earth, then a Pem is a good choice.
About the jumping. No, corgis should not be jumping in and out of the truck. They do quite well with an assisted "boost", though. They are not fragile like many other dogs their height, but they are easy to pick up. One hand under the chest, a "boost" on the butt, and they pop right into their crates in the back of our SUV. As for the stairs on your toy hauler, once the corgi is over one year of age, they can learn to negotiate the steps. Corgi puppies should not be allowed to jump off of beds or furniture, or go down stairs until their bones are set. You can do a lot of "frame" damage by letting them jump too young.
In general, corgis are far more outgoing than shelties. They also tend to (on the whole) have more of a sense of humor. Some bark, others don't. It is not as common as it is in shelties, but there are Pems that bark too much. Early training is the key, as it is with most potential behavioral problems. These are not toy dogs, they are herding dogs, and they need a job to do!