I just went though this (picking pistons for a full motor rebuild). I personally trust what Jeff Ireland says (he really know's his stuff!) and stay lower than 10:1 compression (you'll need premium fuel). You can use a thicker head gasket to lower compression some (add more to offset anything you remove from the cylinder head deck height or off the top of the block), but with your stroker cranks you'll also want to be very careful about piston-valve clearance in your choice. (With that stroke, it's even possible the top of the piston travels past the head-block matting surface.) Jeff also advised not going over 90mm bore diam - and not just for those reasons (gaskets, etc,), but also because cylinder wall thickness starts to get more marginal above that. For hi-perf/race applications, and high heat/stresses that can cause problems. Larger diams obviously get you more displacement, and all else being equal that's better for torque, but the diff in displacement may only be 100ccs more... The larger bore diam may also drive not just more machining of the block, but also the head (see piston travel comment above). Also, with either bore, with the stroker crank, you'd likely NOT be looking at domed pistons, but flattops/notched ones.
My 2cents. HTH...