The BMW 135i convertible is a great starter model for singles and young couples eager to own a Bimmer. It’s powered by the same marvelous turbocharged engine found in the larger and more expensive BMW 335i, and it offers similar speed, agility and handling. We prefer the 135i convertible to the less expensive 128i, partly because it’s available with BMW’s fabulous seven-speed, dual-clutch automatic transmission for just $450 extra. That transmission makes the 135i dramatically quicker than the 128i, in which the automatic is an older and less efficient six-speed Steptronic. The BMW 1 Series, however, is noticeably smaller inside than the 3 Series, with less shoulder room and a very cramped rear seat.