[lifthrasiir]

> I've always used the BSD form, even though I came to Linux much much later, but I guess which form you use comes from where you learned basic *nix commands.

I too use the BSD form but came from the Linux world. Probably it is just a matter of taste (a common answer to everything!).

> I guess the lack of '-' with tar is more apparent because POSIX didn't create a different syntax, and so most people omit the '-' for terseness -- while with ps it would require learning a different syntax.

I argue the ps situation is worse than tar exactly because of that reason. There are three different classes of options in ps, often with slightly different meanings and sometimes with two different long-form options only distinguished by their cases...