12 or 20, no matter. I personally prefer a 12, a pump over an auto, and an 870 over a 500. However, I know that unlike my older (early 90s) 870 Express that was essentially the same as other 870 models, the current generation Express models are a bit down-spec'd and someone posted earlier that the current ones won't accept a standard tube extension. If you're having a hard time making it fit in your budget, I'd definitely look at a used 870, 500, or Win 1300 before I went with some of the off-brand knockoffs. You might even find a police trade in good shape with the long tube already.