Only you can decide if the difference in cost is sensible for your budget.

Bearing wall studs are required to span from the first floor to the bottom of the second floor framing without a splice. That usually means removing the existing ceiling framing, cutting or removing the existing top plates and sistering the bearing studs with new taller studs then adding two new top plates.

You need a price for that additional work from a contractor before you can decide if its worth it.

I have often wondered if a building inspector would allow a 4x4 to be added to the top plates if vertical TimberLok screws were used to attach it to the existing top plates, A ceiling height increase of 3 1/2" is more impressive than you might imagine.

I've moved existing ceiling framing to form 4 ft coffers and put new floor framing on top of that. Here again you need to get it approved by the local inspector.

It would help to know the stud size and how the roof rafters or trusses currently rest on the walls.

Nothing is a no-brainer in a renovation.

The larger your first floor open spaces, the shorter that 8 foot ceiling will appear. Even raising just part of the existing walls and ceiling may be enough to provide a more pleasing space overall.

i meant to say in the midst of a design review with the architect

I have 8 ft ceilings on my 1948 house on the first floor. When we finished the 2nd for and added a full dormer across the back (story and a half house), I had 9 ft ceilings put on 2nd floor. That was only a small extra cost.

IMO 9' is a huge improvement and very noticeable over 8'. 9 to 10 is less of an impact, but I like 10 more than 9

Gotta draw a line somewhere, I chose 9' ceilings

If you will need to remove the entire roof structure in order to construct a floor, and you are making radical changes to exterior windows and doors and interior floor plan, sure go to 9 ft. Level everything and start over. But that doesn't keep within any budget I can imagine.

Have you and your architect explored 1) increasing the existing first floor plate height, and 2) using specially designed second floor trusses with a raised bottom chord as a means of increasing ceiling height without changes to first floor wall studs?

Increasing ceiling height during a renovation is a tough thing to do. Do you have the option to open the ceiling /vault the ceiling instead? This might be do-able in your main living area only.

If your roof is coming off anyway, I would definitely look into raising the 8 ft ceilings. Your location and labor pricing will dictate the added costs. Frankly, I'd rather have 9 ft ceilings in the public spaces (first floor) and 8 ft ceilings in the private spaces (second floor) if it came down to having choose one over the other.

Virgil's suggestion of the floor trusses seems the most logical way to get the extra height without having to take out all the first floor framing to go back up with 9 ft studs.

I just did this on a home by adding a double 1.75" x 11.875" LVL (engineered lumber) to the top plate with a connection detail from the structural engineer to resist the hinge effect. The beauty of that approach was that the LVL also functioned as the header for all the windows and doors allowing us to raise the window and door heads. My 6'-9" client really appreciated that!

If you plan to do this, work with a structural engineer and talk to your building department to make sure they'll allow it.