I have no experience with the Urchin, but I can say Aqua C makes excellent skimmers, their Remora/Remora Pro HOB
skimmer is considered the best HOB
skimmer on the market. The Urchin, I believe is their in sump version of the Remora. I don't think you can go wrong with the Berlin on that size tank either, I used a Berlin Classic to skim a 150g tank (I used a mag 9.5 for the pump) and was pleased with the job it did. Either way you get a good skimmer, this might be one of those win/win situations where you look to the best price for a guide.