Old or new, some gloves have more padding than others. Not everyone uses a heavily padded glove. I'd go to a local shop if I were you and try some on. My full-fingered mountain bike gloves aren't terribly different from my full-fingered road gloves in terms of padding. They do have some extra bits of material on the index finger though for extra grip and durability. I was taught to ride with my index fingers resting on my brakes at all times, so I like that extra bit of material. I'd otherwise wear a hole in the glove pretty fast.

As for riding a rigid mtb, I can't give you insight there as I my mtb have front suspension. You likely will have to toughen up a bit, change your grips and/or work on keeping your upper body relaxed (but not too relaxed) so that you can better absorb some of the impacts.