I currently have a 9" delta band saw that I use  to cut osage staves.  I know it is a little undersized, but I go slow and make it work.  I have been offered an older 10" Rockwell for $50.  Would I gain anything for the money?  Would it be that big of an upgrade?  If not, I could use the money on something else.  I am a budget bowyer.

I would saw to pass on the 10". The best thing you can do if you cant afford a bigger saw is the blade. I use a 9" delta with blades made by timberwolf and it works well for a small saw. I am saving right now for a 14" with roller bearing guides.

i agree, save your money until you can get somethin bigger, the one inch isnt that much of an upgrade. only thing youd be buying is the name there, as long as what you got works for you then stick with it till you can truly upgrade. i use a 9 inch too, and although i dont cut osage staves with it i wouldnt swap until i could go to something significantly better.

There's two things that affect your saws performance the most, assuming the parts are in good condition. A quality blade with the right TPI and a well tuned saw. Suffolk Machinery has some good info about tuning your saw on it's website. This will give you the best performance until you have the $ saved for a bigger saw.