We use the low point system for our series. It works well for us. In the past I sailed in a fleet that used Cox-Sprague. It worked well with a smaller fleet where many times there would only be three boats out but other times there would be up to about ten. The advantage of Cox-Sprague is that it rewards you for beating more people- a first place out of 10 boats is more points than a first place out of 3 boats. This can keep someone for being rewarded for only showing up when there aren’t as many others boats there. The disadvantage is that it is a little more confusing, and, unless you carry a scoresheet and calculator with you, you won’t know how you did until the race is scored.
I use Sailwave for scoring larger regattas, especially if there is a Portsmouth fleet. It works well, but can have a few quirks that take a little getting used to. I tried one or two other free scoring programs in the past, but ended up being happiest with Sailwave. Someone else scores our fleet series; he just uses Excel. (That’s an advantage of the low-point system- it is very straightforward!)