I have a street-driven supercharged 400 Small Block, which is running standard heads with 1.94 inlet & 1.5 exhaust valves.
I have the opportunity to purchase some heads with 2.02 & 1.6 valves.

Could anyone tell me if there would be noticeable performance gains from the larger valves?

Cheers  

there might be some gains....  but there will be an increase of chances with durability issues with the thin areas between the valves.... being a street driven car...  

IF THE HEADS ARE STOCK HEADS WITH LARGER VALVES THE PERFORMANCE GAIN WOULD BE MINIMAL,EVEN WITH POCKET PORTING.IF YOU REALY WANT TO GET BETTER PERFORMANCE I WOULD GO WITH AN AFTERMARKET HEAD.THAT IS MY OPINION.I HOPE THIS HELPS.  

Thanks for the advice. I'd always planned to eventually get some performance aftermarket heads. It was just when I heard about these I thought it was worth looking into. But I agree with your thoughts, and will keep my current heads until I can justify some new aftermarket ones.
Cheers.