The Right Boat
There is a very knowledgable gentleman here, JeffH, who hopefully will explain the attributes that make a boat tender or seaworthy.
Boats of any size can be very tender, that is that they can heel quickly, at very acute angles when the wind freshens. I don''t know your boat but from your dscription it is most likely a light displacement day sailor, perhaps over canvased and narrow beam. Also, it sounds like you have not adhered to the maxim: "reef early and reef often".
LOA of a boat has nothing to do with its performance to weather, seakindly ride or tenderness. Boats with a greater beam and heavier displacement tend to be "stiffer". That said, there are also (again JeffH needs to reply) many other factors that contribute to a boats stability. These are the placement of ballast, hull depth, keel depth, height of the rig, sail area to displament, center of gravity and center of effort.
It is certainly possible to find a 26ft boat that will be much more stable in a blow. You could also get a 40ft boat that will be light and overpowered and terrify your wife.
The final consideration is to balance your desire for a boat that is lively and fast with a boat that is stable and not overpowered. They are around but it takes quite a knowledgable person to find them.
As for the power vs sail thing...powerboats are a means to get you to a destination, sailboats ARE the desitination.
One last piece of advice, with respect, if you are finding it difficult to control a 26ft boat, it might not be the best idea to jump up to a 40 footer. 32ft might be a better choice and then work up from there.
Hope this helps.