Hi there, Im new in this sport, Im buying myself a bike for offroad, but I wont do anything extream with it, I will ride 15 or 20km rides on dusty roads, through wood trails, but nothing too extreme.

Im like these two bikes:
Cube Aim: http://www.cube-bikes.de/xist4c/web/..._id_35831_.htm
Trek 4300: http://www.trekbikes.com/us/en/bikes...4300/#geometry

Now i like Cube Aim better, It looks better, dont know about parts, I guess Trek has better parts but I was at a shop and when comparing these two Cube Aim looked much better build, like it has better quality then Trek.

Now can someone tell me are Cube bikes good? And is Cube Aim good bike for me? Like I said, i will ride it offroad but nothing extream like jumps etc... joust riding through wood paths and that stuff.

Now another question, I know i will bother you all now, but please take some time and help me Im in confused.

What size to take?
My height is 178cm or 5' 10.1"
My inseam is 79cm or 31.1"
My arms, when i spread them, they are 169cm wide, (appe index??) how do you call that? So thats 169cm or 66.5"

So what would be good size of frame for me?
I tried Cube aim 18" and it was ok, but they didnt have 20" in shop so I couldnt test 20" one. What do you think would 20" be too big for me?
Trek 4300 18" was like small under me.
The problem is I dont know what to choose, I never ride any bikes and I dont know how should I feel on bike if it fits me.

And for my way of driving, should i get bigger or smaller frame? I will not turn left or right all the time, i would joust drive through woods.

So can you tell me what frame size would fit me, and is it better to take bigger or smaller frame for my style of driving?

And can you tell your height and inseam and what frame size are you driving?

Guys sorry for big post, but Im so in to this now I dont want to make any mistakes and chose wrong frame or bike.