Yes, short matters. If you can say the same thing, with fewer syllables / less letters, while keeping 2 - 5 in check, it's a no brainer.

Of course, if you can support your long domain, such as "ISoldMyHouse.com" with hundreds of weekly radio placements featureing a "catchy" tune, you can probably drive home a longer name too.

There are no hard and fast rules, but the guidelines that I mentioned above are tried and true.