With Slicehost now being owned by Rackspace, they are more likely to stick around for a while which is nice if you're into that sort of thing. But they are both fantastic, can't go wrong.
Linode has been around a pretty long time now- I've been a customer for least a couple years. I think they're well past the point where we need to be worried if they're still going to be around next year.
Or rackspace could just one day decide the VPS market isn't for them and declare slicehost a mistake, and then shut it down. Not entirely impossible...
Or they could lower prices hoping to attract more people. Or they could deploy the Slicehost guys to work on their own offerings, which don't interest me. Or ... lots of things.
