Unlike cellular phones and personal computers, there is a difficulty

I'd try not to rely on these sorts of idiom considerations at all (see above in this thread for my rationale for this question).

However, if you want to go there, (1) "have difficulty in adapting" is perhaps allowable(?) (I'm honestly not sure, since I don't really do idioms) but certainly wordier and more awkward than the straightforward "have difficulty adapting," and (2) the totally correct "have difficulty" is not the same as the (I'm pretty sure) idiomatically incorrect and slightly illogical (because singular) "have a difficulty."

All that said, my drumbeat continues: Please stop relying on these sorts of considerations. You will never be good enough at idiom and style to get a great score that way. It's not personal -- it's just how to GMAT works. Stop trying to do idioms and what "sounds better"!