Replace SPD pedals for road pedals... which system to choose?
I've ridden commuter and road racing bikes both for decades and can validate your decision to go specific in regards to your shoe/pedal setup.  Start with the shoes - try a bunch on and find a pair that really fit well and seem to work for you.  Most modern shoe/pedal systems use the three bolt pattern common to Shimano and Look systems so there's not a lot of compatibility issues anymore.

Speedplay is the outlier for sure here - I wouldn't worry so much about single sided vs double sided.  Getting in and out is a bit trickier for road systems but you'll figure it out quickly regardless.  What you want to concentrate on is float and release pressure.  Since you're used to clipless on your commuter, it will be fairly straightforward to try systems out.  Work with a retailer who will let you try different systems while using a trainer, that way you can get a feeling for how they work.  If you don't have a retailer close by who will let you do this, look for a fitter and ask them to fit you.  It costs about $100-$150 to get fitted properly with new shoes and pedals on your bike but it's well worth it in the long run.