I use Slicehost, after looking at Linode's pages these features seem to be missing:

Bandwidth is pooled between all of your slices.

Money is pooled -- if you pay a certain amount, you get the "annual discount", but then you can use that for paying for whichever slices each month. And you can bring slices up and down whenever you want to, and pay a prorated amount.

There's a nice API so you can automate a lot of your activities.

On the other hand, Linode does seem to be a bit cheaper on RAM and a lot cheaper on bandwidth.