They are much more similar than different - they are both red early primocanes, both very productive and large, cold hardy and both taste very good
Joan J vs Himbo Top; Joan J is about a week earlier, slightly smaller (but still big), slightly less productive (but overall very productive); it probably tastes a little better (rich and more raspberry-y) and it turns dark red so very easy to tell when it is perfectly ripe; it is a little worse with phytophthora but a little better with botrytis (but neither of these are big concerns)
Himbo top is slightly more productive, a tad bigger, maybe a tad less tasty, less rich (but still very good) and it has a little more susceptibility to grey mold (botrytis) if you have a lot of rain (which means you just have to be more diligent picking them -slightly less forgiving if a wet summer); very good with phytophthora
Gun to my head, Joan J but I love both