I think we are past the days of a constant starting 11, due to large squads, fixture congestion, injuries and of course tactics. It depends on the opposition as to what is our 'best'11. For example away from home against good opposition we need to control the game better and soak up attacks, so the 5 man midfield works well, especially away in europe. At home in the Premier league we should be playing 4-4-2 and going for it in every game no matter who the opposition like we did against the Arse. The 4-4-1-1 is suited to our european games as the pace is slower and more control of the ball is needed, our record in eurpoe since we employed this system has been superb, with only the deportivo disasters last season the blip.
I also think Veron performs better in the bigger games, especially at OT, he also plays well in most of our european away games, but his form on the road in the PL seems to be dodgy. In scrappy games where you have to dig in, like the West brom game, seba is best left out of the team, as his talents are wasted, but i would have in every time we need to go for a win, especially in europe, as he is one of our best playmakers.