Sure, if you want that level of control. In my case, I was happy to not have to implement that part of things. It isn't a trivial amount of work to deal with the credit card / address forms and get everything correct. I made the iframe look like a part of my site well enough that people can trust it and it saves me a ton of development time.
Your app appears to be in private beta, so I can't test that form to see if you missed anything and post about it here. ;-)
we contemplated building a JS solution as well, but using JS can place your site within the scope of PCI compliance. (this is somewhat up for debate) the reason we went with an iframe implementation is because it is firmly outside the scope of PCI, and we are working on making it even more customizable.
either way, you are in good hands with stripe or wepay. (at wepay we are big stripe fans - they rule!) to me, the big difference is whether or not you want the money to settle to someone's bank account directly (stripe), or whether you want it aggregated and stored in an online account first (wepay).
Your app appears to be in private beta, so I can't test that form to see if you missed anything and post about it here. ;-)