I've never tried the pills but I can tell you about the phospho soda. I've tried the gallon of water one, and compared to that, the phospho soda was a breeze. BUT!!... it will make you sick to your stomach for a short time. I never threw up, but I felt like it for about a 1/2 hour after taking it. Once I started going though, it went away. The good thing about the phospho soda is that you don't have to drink a lot of it and it's quick and painless (no cramping). It tastes really yucky, but by adding something like Crystal Light to it, it goes down a little easier.
You should try doing a search on the pill one, I'm really not sure if it's been discussed. Is it something new??
I know you're scared of the throwing up thing... I don't really have any words of wisdom in this department, except to say, I'm sure you'll be fine. We'll all be here for you if you need us though!
-------------------- ~ Rachel (IBS-C)
If life hands you lemons, make lemonade!!