Depends on the shot. Ive got three long lens'. The 18-55mm which i hardly find myself using, my Canon 18-135mm and my Canon 75-300mm for when i was a super telephoto shot and probably my favourite of the three. You can pick it up super super cheap too. so if you want just one id say grab the 75-300 but if you can grab both you'll often find yourself in positions where 55mm is too wide but 75mm is too long thats where the 18-135 comes in handy.