I just bought new gloves. There is quite a difference in hand size between different brands/models. Some ints felt like "little kid" gloves, some were almost as big as the seniors. I'm on the borderline, and some int gloves I couldn't fit my hand into.
There is a noticeable difference in the size of the boards and the length of the arm part in blockers between sr/int. And in the the arm part of the trappers. I actually preferred the feel of the intermediates - the seniors hit the arms of my c/a in a not good way. Felt much less mobile. I'm short, and have short arms, so what works for me won't work for a ganglier sort.
Same sort of thing with all the other gear. Int stuff is for the most part a little less bulky. I've owned both sr and int in pants, gloves, pads, and c/a's that all fit me. Right now I have an int c/a, senior pants, int pads, senior mask, and int gloves, because they were comfortable.
Short version - try a bunch on if you can.