New customer: I need to pick your brains.
Me (cautiously, because I know how unworthy my brains are of being picked): Okay...
New customer: I'm a new knitter but I'm rubbish at sewing up. How do I do it?
What would you say? I told her the truth as I know it: that about 90% of the knitters I know sew up using a back seam. And it's perfectly adequate. But at the same time, the 'correct' way is to use mattress stitch. Bear in mind, this was a knitter who'd been using a bulky overstitch - probably anything was going to be an improvement.
What's backstitch got going for it? Well, it's quick, easy, it's secure and it looks okay on the right side.
And mattress? It more or less disappears on the right side and it's very easy to undo if you find you've veered off the line you're meant to be following.
The cons of backstitch? It's a bit bulkier on the wrong side and especially under the arms where seams converge and it's very difficult to unpick without accidentally snipping the wrong bit of yarn.
And mattress? You need exactly the same number of rows for it to work just right, it's (I find anyway) a much slower process and difficult to do well with your knitting in your lap.
We hosted a Finishing Techniques workshop recently at Three Bags Full - it was great to learn the different techniques for joining that make for a neater, more professional finish. But just because you might know them, you don't have to use them all the time. Don't feel pressured to discount anything. Mattress is great for that special gift - just like a wonderful yarn is great. But if you're happy with backstitch most of the time or want to use a mix of the two - that's fine too. That's my feeling anyway. But maybe I'm just pretty slack!