some reeds are restrictive. the stock 103 reeds from the u1 or u2 and maybe u3 engines had tiny little holes on them that essentially void the effects of any performance upgrades. if you have these get rid of them immediately and reap huge power gains.
If your engine requires huge flow, and you got a huge carb with a huge intake then it can be beneficial to get a bigger reed block.
Some reeds are of higher quality. carbon fiber reeds will spare your engine if they happen to break off, and reed blocks that are rubber coated will seel better possibly increasing crankcase pressure.
for you, it really depends on your current reads, and your setup. if ya got the stock ones, maybe think about upgrading.