In general I believe the Qe2 setup (in the King's Indian Attack) is less effective if Black hasn't committed himself to ...d5. John Emms, Starting Out: King's Indian Attack
One of the best practical features of the Bb5 Sicilian is how little theory there is to learn, compared to the mainline Sicilian. For example, you can be fully prepared for 2...d6 3.Bb5+ in less than the time it would take you to wade through the analysis of a sharp line versus the Najdorf - and that would still leave you with the small matter of the Dragon and Classical systems to worry about. Neil McDonald, The Sicilian Bb5 - Revealed
Spend only 25% of your chess time studying the openings. There are lots of other areas in chess that will make a more dramatic difference in your results - just one compelling example is the study of tactics. Lev Alburt, Chess Openings For Black, Explained
Most amateurs are less at home against 1...e5 (after 1.e4) than they are against the Sicilian. They often resort to a wide variety of dubious gambits against 1...e5, and very often Black can emerge from the opening with an advantage. Larry Kaufman, The Chess Advantage In Black And White