I don't know, maybe my taste for lettuce is not very sophisticated, but I have always wondered about the many desriptions of lettuce from the seed catalogs. They all taste pretty much the same to me. Even head lettuce if harvested as it is forming leaves rather than being allowed to head tastes pretty similar to all of the others. Now, that is not to say thay all lettuces are the same to me. Romain seems to last much longer without bolting and without getting bitter. There seems to be much variation in the texture of the many loose leaf varieties. The bibbs like buttercrunch seem to give a big harvest over an extended season. IMO all of the lettuces can be grown over an extended season if one plants several successions about three weeks apart. Young fast growing lettuce ressists the effect of the heat of summer much more than do older more established plants. Some years I've managed to grow tasty lettuce all the way until the very hottest part of the summer, simply by keeping successions going and planting in semi shade/morning sun only locations in the late spring/early summer.
As a result of my experience with lettuce, I usually overweight my planting of romaine, because of the long season that it will provide. Then I try to plants at least three succession plantings of the more delicate loose leaf varieties. The bibb types also get somewhat of an overweighting because of their heavy production of very mild, large leaves, which continue over a long season. For flavor, well I don't find that in lettuce, all of which are very bland to me. We grow arugula year round and also try to keep a few swiss chard plants going. Add to those the fresh grown peppers, cucumbers, tomatoes, radishes, and the salad has all of the zest and flavors that anyone could want.
One last mention would be of the mesclun mixes. I usually make a planting of those very early in the sping. They don't seem to handle hot weathers as well as the lettuces. I don't think that a mesclun mix contains very many if any true lettuces, but what a spicey, flavorful mix of salad greens. For us it is always a delight to walk out and pick that wonderful mix of interesting shaped and flavored greens for an early spring salad.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.