CS damage all the way. Attack speed isn't as improtant if your attacks are doing 3x thier normal damage. Especially since runes are one of the few ways (compared to other stats) to boost CS damage.
The only drawback is thier cost, which is considerable so plan on blowing tons of IP for only a handful of runes that won't be very effective on other heros (Shako, Gangplank and to a much lesser degree Ashe come to mind as benefiting from CS dam runes).
Also don't worry about the recent "nerf" to CS runes, they did lose some of thier power but overall they're still very, very effective and on a hero like Tryn they're your only real choice.