Alkenes v/s Alkynes in two different reactions

Alkynes are less reactive towards electrophylic addition than alkenes. However, in case of catalytic hydrogenation, alkynes are said to be more reactive. Why? Also, if I want to add H+ as an electrophile, then will alkenes be still more reactive than alkynes?

Does the reason lie in the mechanism of both the reactions (that was obvious, I guess)? If so, please explain, I cannot seem to justify for the later one.

Please, note, than nearby substituents may affect these properties dramatically. Deactivation of alkenes in electrophilic addition by strong $\pi$-electron-withdrawing groups is well known.