Both watches are iconic for the brand. I owned both for a very short while but here are my observations. The Lange 1 bought new from an authorisied dealer had problems with the date change within a week of owning it and I sent it back to Lange for repair. It took about 6 weeks before it was returned to me in excellent condition but with me, I am a bit of a perfectionist and tend not to give a brand new expensive watch a 2nd chance and sold it off. The newly revised Lange 1 however may prove a lot more reliable.
The Up and Down was terribly accurate but the thing that put me off was that it works on a single barrel and required more than 150 turns to fully wind the watch. One could argue that because the power reserve is 72 hours, this needs to be done only once every 3 days but for me it was too much turning (20 to 40 turns per day being acceptable to me personally) so I auctioned the watch off.
Between the two watches, I would opt for the up and down simply because I do not like a date shown on a watch. I know that is part of the Lange 1. Also the slimness of the Up and Down (partly due to the single barrel) is a further attraction to me.
You see a lot more Lange 1s being sold in the used market so in terms of exclusitivity, the Up and Down triumphs. And I apologise to anyone if I am not allowed to say this here but if you are really serious about purchasing one of these watches, organise a trip or holiday to the Far East and you will be still be able to purchase a Lange for much less than the cost in Europe (not sure about the US) even after paying for a good holiday!