They are quite different boats. The Lighting and Flying Scot are racing boats, the Sunfish and especially the Snark are more of a "have fun" type of dinghy.
The Lightning is somewhere between a keel boat and dinghy with a heavy weighted keel. It weighs about 700lbs and would be harder to trailer. I've sailed them and they are a lot of fun, though in most conditions they are more of a two person boat.
The Flying Scot has 191 sqft of sail area, which is a lot to manage on a dinghy when single handing. I haven't sailed one, but I think it's probably better as a two person boat too. Based on it's 850lb weight it must also be a weighted centerboard.
The Sunfish is the first boat that I ever sailed on, but worlds simpler than the Scot or Lightning. It's fun, but I think there are boats that you'll grow more into than this one.
The Snark is basically a styrofoam Sunfish and should be close to free.
I think you'd probably be better served with a Laser (maybe with a radial rig) than any of these. You might also look for two handed dinghies aimed at the juniors market, they can often be sailed well single handed. Flying junior and 420 are two examples.
This is a heavily biased (towards the 505) list of dinghy classes, but I find it useful even to see what it says about other boats. You can learn a lot by reading between the lines:
The 505 is a high performance two person dinghy with tons of sail area, so I don't think that is what you are looking for either.