Scott
IMHO I don't think this question as phrased will get you the right answer because yes, it is about preferences, and no one here can say that this wheel size or HT or FS is best for YOU to race on.
You should already have figured out what works for you and what you're comfortable on. This would depend on the course, your style of riding, and money. You've probably ridden on some H2H courses, so you know what its like, and whether your current set up works, or you need more suspension, or smaller wheels. You should also have a budget.
A more tailored question would be something like "What is the best XC race 29er Hardtail" or I have $x,xxx to spend what is the best XC FS for me to race the H2H courses, or even "what is the most successful XC race bike in the world in HT and FS".
I don't think a forum can tell you that 29er HT > 26er FS for you to race on.
My personal preference is what I race, which is a 29er HT, the GF .:Superfly, and I dig it.