you need forged pistons if you'r reving over 8k really as the std pistons aren't really up to it.
The intruders are needed for high lift/duration cams as the longerover laps reduces the effective CR, so a higher static CR is needed to maximise the actual.
Slipper piston's are designed to be as light as possible to allow them to be used in high rpm engines, 10k+ they do not last as long as they have less skirt whihc causes higher pressures on the skirt there is asn hence faster wear.

slippers are lighter too (plus you need new rods to fit the skirt)

as said above they are lighter and are a lot stronger.i have a set in my 1293 mini.very impressed with them.it hasa 8k rev limit which is a hell of a lot for a mini engine

also better heat treated

slipper pistons are far more robust over standard forged items, its all about the design process with the skirt. highly unlikely you will need these in a corsa engine unless you plan on a 10k rev limit

Depends what spec of omegas they are. If they are the intruder type they will give much more compression. Generally I imagine they will be stronger, whether your engine spec would need this strength I'm not sure.

Slipper pistons, cant really remember but i think its something to do with the piston skirt.

also what are slipper pistons?

what are the advantages/disadvantages of these, over standard pistons?