I’ve been comparing sock patterns and am confused. In the descriptions for ssk, some say slip the first stitch knitwise, then slip the 2nd stitch purlwise, then knit both together. Others say slip both the 1st & the 2nd stitch knitwise, then knit together. Which is better and why? Is there a reason for one over the other?

the first one you described is supposed to be the “improved” ssk. It apparently is supposed to lay flatter. either way is acceptable though.

Here are even more alternatives!

I have an old pattern from the 40’s in it it says to "knit 2 tog t.b.l (through the back loops) this is the second decrease in the row (its actually either side of a set of stitch patterns).

I don’t like how it looks - do you think k2 tog tbl is the same as ssk?

No, it isn’t. Because knitting tbl, whether it’s 1 or 2 sts, twists the st. SSK doesn’t twist them, they’re flat.