asking tech savvy individuals when it comes to engine size; which is more reliable?

38-hp single-cylinder, liquid-cooled Rotax 450 four-stroke
or
a 570 Rotax 48-hp, eight-valve, liquid-cooled

people always say smaller usually means more reliable. But the 570 is a much bigger engine and looks beefier.

These are on the 2016 models by the way

I know they are new, but just from past history