Interesting, thanks for the site! So I'm guessing it is cosmetic? H beam have the sides of them pretty much cut out, and the I beams are solid blocks of beam? Is this right? That's the only difference in the name? LOL..I'm not gonna get into the strength of them here too!!!
They are called H beams because they look like an H, an the I's look like an I, but they are like that for a reason. If you had read the thread that i posted, you would see some trade offs between the two
The cosmetic difference is seen in the cross section cutaway view if you were to cut on in half. Theoritically, I beams are lighter and H beams are stronger, to a point. Not without exception, but that's the jist. Now I think I'll follow that link...
As a genreal street car rule of thumb the I-beams are not as strong as the H-beams.
I was actually at PRI discussing the same thing with Carrillo and Oliver, each feel their design is superior but it is at a completely different level of performance and price.
You could almost certainly be fine with a good quality set of I beams. With the N2O, I would go with H's to be safe, but that's just me. I like over building things. Especially if you aren't building it to have a super high rpm powerband (6000 and up) I'd stay with the heavy (& heavy duty) H beams.