Generally I like 1.1 and that is what my conversion setting is. 1.2 is fine except for some fonts and even there I don't care enough to reconvert, reload etc. I just change the font on the reader where available or carry on reading. 1-3 more lines per page is not a big deal to me.
But for my vision impaired friend with a big font, it seems he likes 1.0 and it often gives that one more line per page. With only a few lines per page one more is a lot
Helen