If you have time, sure do both. If you are crunched for time & cannot do 2-3 QBanks (UWorld + COMBANK + COMQUEST) I would vote UWorld.
UWorld is more difficult (which is good), has better explanations, is (probably) more comprehensive, definitely has less errors, & will prepare anybody thoroughly well to take either board exam.
The only thing I would recommend anyone doing is taking a practice exam a few weeks before your test date (my school required us to take 2 back to back, one from NBOME one from comquest.) That is all the familiarity you really need to "get used to" comlex question styles (IMO.)
There is ultimately no right/wrong answer as long as you learn the material & learn it well. But, I will say that there were several threads on SDN come board season last year from those who only used DO question banks all year/up until comlex, who were startled to find that they were at risk of failing step 1 based on their practice exam scores (despite already having taken comlex) & were getting wrecked by UWorld (despite performing well on comquest/combank all year) only a few days out from their step exam. This was not the case for those that used UWorld all year/most of dedicated & crammed combank/comquest before comlex. It's a lot easier to go from using UWorld to using combank/comquest than it is the other way around, & I believe there is a reason for that with respect to quality/content of the material contained within the QBanks.