What best variety for making fresh (not canned) salsa, best taste /texture?
Oh wow only ONE best for salsa? Don't think that is possible.
Just as there are likely 250 recipes or more for salsa there's likely 250 varieties or more that will make great salsa.
Depends on how juicy/thin/thick/chunky etc. you like salsa. Some folks prefer to use paste tomatoes, some prefer slicers, some use only cherry types, and some swear the only real salsa is made only with tomatillos.
Personally, just as with great sauce, IMO great salsa comes from using a mix of varieties. Gives you a much more complex flavor and texture. Wife won a fair ribbon for her's a few years back and probably had at least 8-10 different varieties in it. Can't recall for sure what all we were growing that year but since we always grow San Marzano, Rutgers, Big Boy, Black Krim, and Champion among others the odds are they were all in it.
Same goes for color. Many discussions on the Harvest forum are about the great salsas one can make using a variety of colored tomatoes.
As with tomato sauce, the best salsa comes from the best tasting tomato, not from a particular type. If you have a slicer you love, that will probably make a great salsa. Personally I like a tangy tomato, not the 'sweeter' varieties. In salsa, the taste should be bold, because it's mixing with other ingredients. You could mix a red and a yellow just for appearance and get a great salsa - anything goes.
My favorite Salsa mix is Kelloggs Breakfast mixed with a good strong red or pink like Brandywine or one of the heart varieties. So pretty, and whatever your best tasting tomato of the year is, mixed with KB, which is always good, makes an awesome combination.