"and Barry which would be your favourite recording?"
Well, I like two live performances from Kent Nagano. The first one is a "pirate" of a live concert in Hamburg, and other one I've heard is on the Montreal S.O.'s website. Nagano takes the first movement a bit over 23 minutes, which sounds just right to me, but then keeps the finale slimmed down to 17:15 or so. Jansons/Oslo Phil./Simax does the same thing, but the 2nd Nachtmusik is a throw-back to the days of taking over 14 minutes for that particular movement. Today, most conductors seem to do the fourth movement in the 12 to 13 minute range, and I really prefer that. As I recall, Nagano takes around 13 minutes.
But in terms of just walking into a store, or going on to Amazon, etc., I would say either Barenboim/Staatskapelle Berlin/Warner Classics, or the new Jansons on Simax. Many people are big fans of the Gielen M7 on Haenssler, but Gielen fails to pick up the tempo in the back-half of the finale. His timing ends up being a bit over 18 minutes, and it just sounds a tad heavy and lethargic to me. If I were going to pick a Mahler 7th with an 18 minute finale, I would go with the Zinman. I like his a lot, in spite of that 18 minute finale.
I have a "pirate" of a live Gielen performance in Berlin. The timings are pretty much identical to his commercial recording, except that the finale is a full 45 or 50 seconds shorter. Believe it or not, that makes a pretty big difference in how it "feels".
Here's a big problem or trap with Mahler 7: many conductors who take the first movement slower (which I like), also take the finale slowly. Conversely, those who have zippy finales, often times take the first movement real quickly as well. Here's an idea: start the symphony out on the slower/heavier side, and then gradually gain speed as you slowly move towards the sun. What a concept!