ᐅ "Large House" vs. "Small House" + Outbuildings

Good evening,
we had our first appointment last week with a local construction company, and we were so positively impressed that we probably don’t need to look for any other companies, but that’s a different topic...
Today, the architecture department sent me the first draft of the house type we discussed. The more we look at the floor plans, the less certain we feel.

So here is the question: We have two house types from the company to choose from and are undecided because with the smaller house, adding an outbuilding (e.g., behind the carport) might be financially possible sooner or later (about 20m2 (215 sq ft)).

About the types:

House A
Single-family house, gable roof, brick facade, approximately 125m2 (1,345 sq ft), 5 rooms

House B
Single-family house, gable roof, brick facade, approximately 114m2 (1,227 sq ft), 4 rooms

Both houses are constructed with solid masonry and some extras (roller shutters, underfloor heating, walk-in shower in the guest bathroom, etc.) at a cost of about 1700€/m2 (approximately $158 per sq ft).

We currently have one child (about 1 1/2 years old), and a second child is neither planned nor ruled out.

I am a passionate musician and occasionally enjoy a half weekend gaming session on the PC. So an outbuilding like the one described actually makes more sense—maybe it could also be used as a party room?! Also, my wife prefers the layout of the smaller house significantly more.

I’m curious to hear the opinion of the “collective.”