Yes, as Clifton noted above, but additionally the other equipment spec (e.g. seat, handlebars), your position on the bike in terms of comfort and control, and handling characteristics (such as derived from a longer wheelbase, or more stable steering).

The gruppo merely changes the gears, and while some offer crisper shifting, or more amenable controls (e.g. Gripshift vs. trigger shift types), greater longevity or lighter weight, all that is easily changeable. You can swap chainrings, rear cogsets, shifters and derailleurs. A poorly fitting frame, on the other hand, or a bike that simply doesn't feel right because it's too short or whatever, is a more durable problem.

Go to a Bike Shop and Look.

My 2001 Cannondale Bad Boy project will have 10-speed Cyclocross double gearing(46-28) and 700c x 25 carbon disc wheels....yeah, I like 'em LIGHT!!!

Ok, so generaly speaking, what are the practical diffrences of a MTB and a rece group? that´s the base of this difference and what for

As Dan515 mentioned in the first reply to this thread, the lower gearing of MTB gruppos is designed for lower speed climbing over uneven and loose terrain, while a road bike gruppo is generally higher geared, designed for a narrower range of circumstances as encountered over paved roads on narrow tires.

Additionally, road gruppos are generally lighter and focused on precision shifting, whereas MTB gruppos are designed with crisp shifting as well, but additional focus on withstanding the dirty, physically abusive world of off-road riding.

Of course, the shifters are different between MTB and Road bikes generally, to accommodate the different shapes of handlebars and conform to custom, and the brakes different to accommodate wheels and frame mounting options.

It's more typical to find triple chainrings up front on MTBs along with long cage rear derailleurs to accommodate lower gearing. Road bike gruppos often emphasize aerodynamic styling and higher levels of detail finishing, while MTB gruppos often go for a more rugged look.

In practical terms, there's not a lot of distinction for most cyclists; one can ride Road gruppos on the dirt and MTB gruppos on the road, it just depends on needs. If you've got a lot of hills, need to pull trailers, or have weak legs, those things might recommend using an MTB gruppo (or road touring gruppo); if your terrain is flat, you're focused on speed, or want the lightest bike possible, those may be things to suggest a Road gruppo is the way to go.

In sum, I don't think you need to be worrying about the type of gruppo at all. You don't have the experience or focus to make any of the distinctions meaningful, and the bike designers have already made the important decisions for you with the bike spec. Just focus on the total package, and get the bike most fully satisfies your needs and desires. If you're riding road, get a road bike. If you're riding trails, get an MTB. If you're cruising around town just to get some fresh air and a little exercise, get a comfort bike. If you want to do long distance touring, get a touring bike.

Stick to the macro questions, and you'll be alright.

Thanks so much!

This. You're way overthinking the issue. If your choice is down to those two bikes from the other thread,and you can't physically test ride them both,then measure yourself and compare the geometry charts of the bikes to see which will fit you best.

For typical road commuting, MTB gearing is often too low and road race too high.
I found that a midrange touring style setup is just about right for everyday use inc hills.
You can mix road shifters with MTB rear mechs like Deore but NOT MTB front mechs.
Tiagra front mechs can work with midrange chainrings, eg 28/38/48. Some versions can be persuaded to work with even smaller rings.

Depends on your "style" and personal preferences IMO. I use a montague paratrooper with fenders and a back pack for most things, otherwise I slap a rack on it, and load it with a lot of stuff whenever I'm gonna run out for groceries etc.

I like being a little more upright, and the folding aspect means that I can bag it and take trains if I have to.

Ok, I am going to focus on that, when riding a flat bar road like these ones, should the arms be totally upright when handeling the flat bar? in the willier the arms felt a bit more relaxed

The bars should be high and close enough that you don't ride with your arms straight.

the difference is FIT, not brand. the Staff at the LBS should be able to sort out getting the fit right.

^^^What he said. If you can't ride both bikes,ride the one you can,then compare the geo charts of the two to see how the other should fit. Print the other's chart out and ask at the LBS if you need help.