Fitting question for first trekking bike - differences in stack and reach I understand this might be a pointless/dumb question, but as an bike freshman, I am confused:

Trying to select an entry level first bike (cross/hybrid) and so far I'm between two of them (local EU brands)
I'm 176cm, inseam 74cm. For the first one, i fit better on their 18'' model and on the second one on their 19''.

I tried both of them on a LBS but unfortunately not for an extensive ride - just a tour around the block. However, their frame geometry is quite different,  having:
Stack:518,2 mm
Reach:383,5 mm

And  having:
Stack: 497,7 mm
Reach: 394,6 mm

I enjoy upright riding position and I favour stability and comfort more that speed. With these in mind, am I wrong to assume that the first one is a better option for me? Will the difference be too noticeable?

Thanks a lot.
Impossible to tell you whether a couple of centimeters either way will make a bike fit you better. A slightly lower bar may actually suit you better than a higher bar, even though you value comfort over speed. You might feel slightly more stable with a little more weight on the front wheel.

Honestly you just need to ride the bikes back to back and make a decision as to which you feel comfortable with.