Knitted stockinette stitch loses it's definition better than garter, which appears a little bumpy after felting. However, the edges roll with stockinette so depending on what you're making, you may want to garter or seed stitch the edges of the item. For bags, I find a kitted-on i-cord looks best for edges. I don't crochet but I imagine that if you do it plainly it should be OK. There seem to be more free patterns for knitted felted items than crochet. Try Knittingpatterncentral.com and Crochetpatterncentral.com for free felted patterns.

There also is a "Booga Bag" pattern that uses Noro Kureyon yarn. I've used that yarn before on a felted bag and it turned out great. It was just a big square bag with handles. I gave it to my neice for her birthday and she uses it as her knitting bag. I think you can get the Booga Bag pattern off the internet. I haven't tried it yet, although I have the yarn and someday I might get to it.

Felted stockinette gives a smoother fabric but I like texture so I often use other stitches. I strongly suggest that you felt a swatch before starting your project. From the swatch you will learn how fast the yarn felts and if you like the texture. You will also learn a lot about how your washing machine felts...felting in a front loading machines takes a little more effort than a top loading machine.

Here is a link that might be useful: Confetti Creative Knitting

I just finished a pair of crochet felted clog-slippers for my daughter and the finish is a bit knobby, and furry looking, I felted a poppy earlier this year and it gave a very smooth appearance. Personally, I like the furry look and will probably felt most things in crochet from now on. I had to wash both of them twice to get the size I wanted.