Hi, I'm changing from mountain bike to road bike, I have three possible bikes, Trek 1.2, Specialized Allez Sport or Lapierre Audacio 400, the first two have Shimano Sora, and the Lapierre comes with Shimano Tiagra, I know Tiegra is better than Sora, but wich one do you think is a better choice?

I really appreciate your help!

have you tested any?
All being equal, pick the one with the better parts

I'm not sure about the Specialized or the Lapierre, but I rode a Trek 1.2 at my LBS recently and loved it. I ended up buying the 1.1, which is a step down, of course, but I still love it. I'm guessing you can't go wrong with any of them, so find the one that speaks to you ...

If I was asking this question it would go like this.....I have X dollars to spend. What are some good bikes? With all the resources available here you might find some excellent deals.

All 3 of those bikes are very nice. It really boils down to which one you like the most. If you like all of them equally than buy the one that you can get for the lowest price. I am assuming that the Lapierre is a little more expensive since it comes with higher specs. If they are all the same price than go with the Lapierre.
There are also plenty of other bikes in that price range that you may want to check out. Giant and Felt are two that stand out and you could probably pick up one of those with better specs for less money.
Whatever bike you do buy make sure that you get a good fit from the shop. I too came over from mtb and I find that the fitting is far more important for the road bikes.
Good luck with your decision.

Thank all of you for the quick response, I'm going to go with the lapierre.