You're approaching this project like a true pro, the same way the big boys do, and they've been doing it for sometime. Many online entrepreneurs just place advertising or implement a new marketing website concept, watch it fail and assume it can't work, when it may have just needed a little tweaking, like adjusting the knob on a radio to bring a station in much clearer.
Split run testing can be very effective when following the right guidelines. I believe you're referring to the mini-website concept, when you state you are going to use one page instead of four.
"Caveat' Emptor." The caution I suggest is to test this well, because, though this website design has historically been very effective over the last few years, they are all starting to look pretty much the same.
Ever since the e-book "How to make Killer websites" (title is something like that), the Net marketing community has implemented in force. This can be a good thing, but as Andrew just stated about squeeze pages, may apply here, they are ALL starting to look pretty much the same.
If this is the reality, the marketplace may become hardened as to this design, dramatically reducing it's effectiveness. I'm trying a new twist to the old concept at http://tradeswin.com
Same concept but a different look actually showing the product near the top of the page.
I've been around since the first caveman first hung his "For Sale" sign on the first "wheel" for sale, OK, I don't believe there ever where cavemen, but, what works today, may not work tomorrow. That's why market analyst have a job for life. Ongoing testing in mandatory for continued success.
The mini-website design was a great idea when it first surfaced because it was new and gave the appearance of NEW Insider information, presented in a relatively new manner.
BUT, after a while the public seems (my experience with them) to becoming desensitized toward them. After they've made a purchase from 1 or 1, they often start to realize it's just the ole "Information online, in a written format.
Infomercials still work, but are not near as an effective advertising medium as they once were. I have traced stats on this and seen the diminishing results as to their effectiveness. I've down two myself.
The bottom line? Test the conventional approach with your product. You may be the exception and the typical design format may work for you. Or, consider adjusting the format like I'm doing with tradeswin.com until you make it work. I personal research seems to indicate, "content websites," are gaining ground for traffic.
People come on line for "information," not a sales pitch. Thus it's getting more difficult to motivate them to read one, once they "identify" it as a sales pitch, and I believe this is what may be happening to the long form mini-website concept.
One observerís opinion!
Keep advancing your project toward financial success.