Mountain Bike Racing - Benefits of going 2 X 10...anyone?

I currently have 3 X 9 and thinking about upgrading to 2 X 10. Is that an upgrade? What are the benefits of doing that? What are the drawbacks of switching to 2 X 10? What chain ring combo works best? I ride a 29er. Any advise would be great! Thanks in advance.

When I first went 2 x 10... I actually had a lot of problems finding the gear I wanted. Now that I'm used to the bike, I've gotten a bit better. I actually shift a lot less now than I did before.

Gearing is pretty personal... If you find there is a comfortable cadence gap then you should explore options... for sure you don't need to go 2x10 todo this... adjusting the chainring up front and the cassette out back can give you a good range.

I have doubles or singles on all but one bike (full suspension Marin) and was contemplating the difference during today's ride with my compact double. The drawback to the double for me is not having gearing that is closer ratio than my current setup on the Salsa Vaya. What I mean is I often would like a gear (resulting in a comfortable cadence) that would be between what I was in and what I am in! Not a big deal, but when you are into the wind or tired sometimes it can be bothersome. This is assuming you do what a lot of the doubles do today and that is to try and make up for a little of the lower gearing by adding a larger range in the rear - with more spacing in-between. With a triple you can keep the number of teeth in the back to a closer ratio.

28/40 is my recommendation however it's a personal thing.

I race my 29er with a 2x9 setup 36/22 and it works for me on a variety of terrain. Its also a cheaper option than buying all new 2x10.

Lighter weight and crisper shifting.
Don't notice the loss of that tiny granny ring at all.
I have Sram XX and was used to XTR over the years but now it's Sram all the way.
Except for those darn XX brakes.
Ohno

I found changing to 2 x10 I was not even worrying about changing gears on the front. For example, at one of our local 24hour races, its a relatively flat course with most climbing coming in the way of false flats. I would normally race the whole course on just the big chainring. But when I had some front deraileur problems I was stuck with just the small chain ring. I was able to put out the same laptimes. It just meant I rode the course a bit differently, slighty less top speed on the flat fireroads and having to use a higher cadence. There's usually enough range in a 2x10 that you can forget changing them and either opt for a spinning or stomping day out on the bike.
So I like it because it not only saves a bit of weight around my crank it just leaves me with one less thing to have to worry about.