A lot of benefits from changing to 15" aftermarket rims.

Plenty of good tyre choices and cheaper too.
Better ride comfort.
Better fc.
Better looks (subjective)

But only get original rims like konig/advanti/lenso/enkei tuning. This rims should be lighter than your current rims. Most importantly, get the correct width & offset. If you get rims which are too wide, your tyres will scrub your fenders.