I have a galaxy s which is ok out of the box but is in no way perfect. Far from it really.
How neardy do you want to get.?
There are lag fixes for the sgs which are ok and speed things up a touch. There are custom roms out there that you can install over the stock android os and this will make the phone fly. Way faster than an iphone and way faster than most phones on the market imo.
Like I say it depends on how neardy you want to get and how much bottle you have got as replacing the stock os and bricking your phone will void and warrenty.
Iphones just work and work well out of the box.
You can do a lot more with the sgs.
Try these fella’s. A wealth of knowledge and shite loads of themes apps and hacks.
Depends on what you want the phone for.