From what I've read, 304 has a slightly higher TCR value than 316 or 316L, which supposedly makes it a little easier for TC mods to do their thing. Proponents of 403 point to its substantially higher TCR value as a main reason for using it instead of 304 or the 316s.Cheech knows better; he‘s tired from bunny watching.
316 and 316L are alloys, as all stainless steel. They contain a little—about 2%–molybdenum to make them easier for welders. It is expensive, so 316 alloys cost more per foot than 302/304, which has no molybdenum. Both work very well for coil building. I use both, but mostly 304. There are other ss alloys I haven't tried yet.
These include 430 and 434, which seem to have a small but loyal following among coilers.
304 is commonly known as "18/8" for the percentages of chromium and nickel in the alloy.
If you have good, modern stainless steel flatware in your kitchen drawer, it is very likely 18/8.
Wire size is another matter. I've used awg. (American wire gauge) 24, 26, and 28 so far. I suggest 26 for early attempts. Then you can decide if you want to play with
thinner wires. Cheech's 0.015" is very nearly awg. 26.
I dunno. I just read.
That said, I've been using 28 ga. 316L for TC and it works well enough for me. Also have a spool of 26 that I haven't tried yet. Might try something else when they're gone, but that could be quite awhile...