Get one which fits you. In the Brooks range, for me, that's the Team Professional (or the B17 narrow) rather than the standard B17. Do not believe the rubbish about 'breaking in' a Brooks saddle. It's either comfortable from day one or it isn't, and if you apply leather softeners to it all you'll do is end up with a wrecked saddle.
Brooks do get more comfortable with age because they do gradually mould themselves to your personal shape, but if they aren't comfortable to start with you probably have the wrong width for you..
The other thing to say is while I used to swear by Brooks Professionals and at one time had them on all my bikes, they're extraordinarily heavy - about 550 grams. When I worked out that the saddle was 6% of the total weight of my race bike I experimentally bought a Selle Italia SLR, which weighs a quarter as much. And although it looks like an instrument of torture it turns out to be (for me) equally comfortable, so much so that I've given away two of my Brooks and the one that remains is on a bike I don't use that much.
Don't get me wrong, Brooks are great saddles. But even the (scarily expensive) titanium railed ones are heavy, and do you really want to be lugging an extra 400 grams up every hill?