It looks like you're new here. If you want to get involved, click one of these buttons!
I'm bound to get hit in the head for some things but I'll try to be fair.
SOTs are generally more stable (surfskis not being included in this discussion). They are technically easier to get back on but strength or other physical issues can still make re-entry a problem for some. They are generally better for fishing due to handling gear and better if you need to get in and out a lot along a shore or perhaps for diving. They are often wider which while it helps stability can hurt speed and handling in rougher waves.
SINKs are better at letting the boat be and extention of your body to give better control especially in rougher waters. You sit lower which gives some stability to offset what may be lacking by being narrower. Being typically narrower they tend to be faster (again I'm leaving surfskis and similar SOTs out of this for now). Being "inside" gives you some additional protection from cold especially wind. SINKs generally require more skills for rescue and balance but gaining those is often part of the fun.
In general only SINKs that lack bulkheads (like many small recreation types) are easily sinkable. So in the category of very cheap boats the SOT is often less sinkable.
Both come in a variety of lengths and widths so one must adjust everything I said a bit for each boat.