would this be your first true track frame? i would definitely recommend steel. keirin is a type of event, involving 3 motor paced laps, and two all out sprint laps. thus, frames designed for this are more suited for short sprints, but not comfort (relatively) on higher lap count races. a 6 day geometry track frame might be ideal, as it is designed to work well in various events and what not. most off the shelf track frames are typically 6 day geometry frames.

i ride lugged columbus on the track and love it.