Opinions please. What do people think is a better investment: an extension to maintain 4 bedrooms and add a bath to a 1-3/4 bath home or remodel to 3 bedrooms and 2-3/4 bath and possibly a small office?

Background: Family with young child live in a family neighborhood in Seattle. Our home is a 2300Sq ft. mid-century. Currently we have a large master bedroom, a smaller family bath and 2 smallish bedrooms on the main floor (one of the bedrooms is being used as an office which we store a lot in). Our attractive daylight basement has a large bedroom (used as the guest room) and 3/4 bath. We do not anticipate having more children and do not have plans to move within 10-years.

We are deciding what would be a better future return option for us:

1. Remodel the 3 exisiting upstairs bedrooms and 1 bathroom into 2 bedrooms and a master bath with either a 3/4 bath or powder room + small office. Or

2. Do an extension off the smaller bedrooms to add the 2nd upstairs bath to maintain 4 bedrooms.

Appreciate any ideas!