First of all don't start with A320s, get 737-700 instead! they are smaller and use less gas (I don't go over 150 seats without some good internal traffic... Also think about EMB 190s/195s! they are great too!) ground connections don't matter much (It only helps of you if you fly to other airports like a few hundred KMs away...) I would go for more slots cause when your airline gets bigger you need slots.
So I say pick daveu.
Also (since you are new...) Don't give up! I lost so many airlines cause I gave up. Keep pushing you will make it! if you need help start a topic here.
One more thing: I see you were thinking about AirwaySim too, You will like it much better here and I hope you have fun! :D
Go for Devau you will have more freedom trying out the game.
However I suggest you first get 4-5 Bombardier Dash 8-Q400A. Now connect airports within Columbia to Bogota and 100%you will have positive profit and from now you can explore the game
Slot availability is crucial for success, so try to find an airport with as much slots free as possible without strong competition. It is difficult to build up a hub-and-spoke System with only 50% free slots. => Devau
Don't underestimate domestic demand. For instance my Airline in Nigeria operates 6 737-900ER just on the Lagos-Abuja Route. So I advise against using turboprops in anything but tiny markets. It hurts your image too much. Starting with 737-700 (or EMB 195) on the better domestic routes sounds like a good plan to me. It will also give you a ORS rating advantage over the competition, that is currently using Dashes.
Jumper, you learn something new every day. I saw airline subsidiaries but didn't know you could set them up only in unrestricted rights countries. So, RESET we go... fortunately I only lost 24 hours. Thank you for this suggestion.