Let me offer some insight as someone who was "brought up" in the information marketing industry.
Ultimately, as the others have said, you're going to need to test (never stop!). However, let me offer some guidelines you might consider, so you can shortcut your path to success.
On the topic of multi-page versus one long page, the long page almost always wins. Every time you make the user click, you're going to have a percentage of them drop out of your funnel. You can feel free to test it, but I am pretty confident the long page will win. This has been proven time after time after time, even though people always tell me they'd never read it. You know who wants to read your info in an uninterrupted fashion? The most interested prospects - the people who are going to buy from you. If the info is important enough to affect their buying decision, get it on that page.
On the topic of simple vs rich page, as Jason said, in B2B you're still selling to another human. No different than selling to a consumer, no matter what "they" will have you think. As such, don't let useless graphics and designery get in the way of your sales message. It took years for that doubleyourdating.com page to get beaten by a different design, and I'm pretty certain they changed it due to Google quality score meddling, rather than conversion issues.
Additionally, the landing is really just a piece of the overall funnel. It's the front door to your sales funnel, and the good info marketers are pros at what happens once someone steps inside. The quickest way to get conceptually up to speed with what to do next is read "Influence" by Cialdini, then think how you can apply his 8 psychological triggers in your follow up sales.
I see a lot of software companies miss the mark because they never follow up with any sales messages once you sign up. If you subscribe to the idea that you will maximize sales only by letting us use your software, then you'll be missing your potential.
In the end, I'm assuming you want to maximize signups or sales, so you'd do best by making that the only option. Eliminate any other distractions. Focus on what the prospect would need to learn to feel a fire under their ass to sign up.
There is more, but I don't want to blow hot air without knowing more about the situation. Hope this helps!