Size bike - Geometry

[BeR]

Help me to choose the right size bike. I know, the best is to do a bike fit...

I am on the market for a new second bike (will sell my actual first Propel and keep my Hygge Model S).

I am 178 cm and saddle height of 74,5 cm.

My propel is in size M with a 100 mm stem and It fits perfect to me (maximum spacers height but I could remove one or two for a more agressive geometry).

My LBS can have a deal on a Spe SL8. According to the size chart, 56 is for me but I think that 54 is more the same geometry as my Propel (but too agressive ?) :

https://geometrygeeks.bike/compare/giant-propel-advanced-pro-frameset-2025-m,specalized-tarmc-sl8-2023-54,specalized-tarmc-sl8-2023-56/

Which size will you recommand and which length of stem for the SL8 ?

Thanks.

[KopytoNieBladzi]

Help me to choose the right size bike. I know, the best is to do a bike fit...

I am on the market for a new second bike (will sell my actual first Propel and keep my Hygge Model S).

I am 178 cm and saddle height of 74,5 cm.

My propel is in size M with a 100 mm stem and It fits perfect to me (maximum spacers height but I could remove one or two for a more agressive geometry).

If you have a bike that seems to be a good fit I'd say to use it as a starting point and try to compare some geos using ,,Bike Insights,, website.
It helped me before and now to pick my 90% chiner gravel