Piper Jaffray analyst Michael Olson says Priceline (PCLN) has the most favorable risk/reward in the online travel space given its "attractive" valuation and exposure to broad strength in Europe. Travel industry trends in Europe during Q3 indicate a solid quarter while U.S. trends showed mixed results, Olson tells investors in a research note. He believes the recent selloff in Priceline presents an attractive entry point. The analyst reiterates Overweight ratings on Priceline, HomeAway (AWAY) and TripAdvisor (TRIP). Olson keeps a Neutral rating on Expedia (EXPE) saying the valuation "appears full" compared to peers.