While it depends on your hold time a bit, if you're looking for a long term book to enjoy (and a good investment) I REALLY don't think it matters, anyone should be good for appreciation (and they're both just awesome books)
If you wanted to buy a book to turn around and sell, well Showcase 4 is probably a bit less risky that 22.......
Anyone see there are 2 or 3 copies of Green Lantern 1 (blue 6.0, blue 8.0 and purple 9.0 i think) and 2 or 3 copies of All American 16 (atleast one blue) RIGHT NOW! That's a lot of prestige GL books!!