The seat angle on LH is a non issue really IMO - not sure why people are whining about it. The seating plan on OS would indeed allow you to sit solo in a window seat, and your two companions in the middle seats. Also agree that VIE is an easier airport to transfer through (unless you're HON or flying F), and with a four-hour layover you could pop into the city for a coffee (train is 4,40 for one or two pax, don't take the City Airport Train but rather the S7 line). Two hours is ok in FRA too.