In our evaluation of both products we went with RPGsp. Both are good products and have outstanding tech support. RPGsp is geared more towards the RPG programmer in that you can put RPG code anywhere in html so we were able to get up and running a little faster. With WebSmart you have to learn their PML language.
Both companines allow a 30 day trial of their software. My advice would be to download each one and play with it to see which one works best for you.