I like the P21S better in terms of drying ability, but I like the Absorber better in terms of size and durability. My P21S towel fell apart, whereas my Absorber just keeps on going. At $6, it's a steal!
I've tried the 2 that you have mentioned. I liked them both till I tried Wizards water Bandit. The Bandit was better all around. Try a search and I'm sure you can find dealers and prices if interested.
My P21S towel's 'skin' started flaking a bit after being put through the washing machine a few times. Like RH said, the absorber's size and durability make it a much better choice. However, I do like the Water Bandit better than both and I also like the Big Blue towel from CMA better than all of the above.
I've used an Absorber for years and I love 'em. After years of abuse, it's finally starting to show some wear and tear. Oh well, it gave me great service. At $6, I'd certainly grab one or two more. I only wish PepBoys would build a store around here. Never tried the P21 towel, as I never really had a need to.