The fact is, with its appearance, texture and taste nearly indistinguishable, Butter, Boston and Bibb lettuce is ostensibly the same variety known under the category moniker: Butterhead. Bibb, however, is a slightly smaller version of the variety and is the first of this cultivar to be grown in the U.S.
For this reason, leaf lettuce is generally more perishable than head varieties; you'll often see it in "baby lettuce" mixes because of its tenderness. Red leaf has a burgundy tint and mild flavor, similar to that of green leaf. To avoid instant wilting, postpone dressing leaf lettuce until just before serving.