I've been thinking about this thread for a while now as it's a very interesting question. If we're going strictly by the OP's question of 'Who had the better career?' then the answer is clearly Aldridge based on longevity alone. His nine years in Portland allowed him to leave his mark all across the Rip City record books.
However, if we're discussing who had the more memorable career, then I don't think the answer is quite as clear. While Roy only played five seasons in Portland, he provided so many more moments that will live in the minds of the maniacs forever. I should also note that I was never a huge Aldridge or Roy fan. I liked them both but neither will crack my Top 10 favorite Blazers of All-Time list, so I don't have a bias either way. But there is no denying how vital Brandon was in reviving this franchise. We were the laughing stock of the league and he made us relevant again over night.
Off the top of my head, B-Roy's delivered these memorable moments:
And here are LA's memorable moments that I can think of right now:
While LA's back-to-back 43+ point performances against the Rockets in the 2014 playoffs meant more than any single moment that Brandon delivered, as it helped Portland do something that Brandon wasn't able to accomplish - get Portland out of the first round, I just don't think he left the lasting impression that Brandon did.
To me, I believe we got the most out of Brandon. LaMarcus, on the other hand, could have been even better; a game changer had he played with the aggression he displayed during that three month stretch of the 2010-11 season.