I always preferred Hitmonchan. Both in design and usability because of a combination of having a unique ability called iron fist and with those three elemental punches. Hitmonlee is just so plain because he doesn't really stand out because of his really basic appearance and standard fighting type stats. I would choose Hitmonchan any day.
Hitmonlee learns some pretty badass moves, most notably High Jump Kick, and overall tends to be stronger but that come at a price of accuracy. I personally took that risk early on, but I've slowly crossed over to Hitmoncha- Sawk. It's all about Sawk
Until gen 4 though all of those attacks are incredibly weak. Fire, electric, ice and i ton of other types in gen 1-3 are based off of the special attack. Hitmonchan has great attack but his special is atrocious, so having type advantage is useless because all of the attacks are still weaker than a good neutral fighting move.
Almost none if those things even existed in gen 1. Like I said, he has the elemental punches, but they are literally useless since they are all specially offensive attacks and Hotmonchan's special attack is awful. Hotmonchan sucks in Gen 1.
Well, I'm a total stat-nerd and all the elemental punches before D/P/Pt counted as special attacks, and Hitmonchan has a giant turd for special attack. I usually go for Hitmonlee because his attack stat is slightly higher than that of Hitmonchan.
i see what would happen if you chose hitmonlee. with a punch, you control the thunder,fire, and ice. But with a kick, you're just a dumbass who lit himself on fire, paralzed himself, and finally stubbed your toe, while getting frostbite in the process. the choice is yours.