S3 slower...clean install or custom rom?

Hello there.

I have a i9300 for a year now and I've been doing the official upgrades by wifi, currently with 4.1.2 rom. Problem is I find It slower over time , especially opening contacts and multitasking, the redraw and reopen of programs takes some seconds, which is irritating. I know that having only 1gb of ram dosent help but do you believe doing a clean install would help? Or should I try a custom rom? I would very much love to install a custom rom but I read that some stuff don't work at all with them, is that true or is there one that is flawless that you recommend?

Thanks for the help. :)

Cheers