A bit of history here first, In the middle 1870's store bought mass produced national brand yeast came on the market. Before that one used either a homemade yeast, a local product or the foam off the top of the beer from the local brewery.
The new store bought yeast came in a tin-foil wrapped, compressed cake that needed carful storage or it would go bad.
In the 1920's the freeze dried pacage yeast came on the market and was easy to store. Yet the cake yeast did not disapear from the market, it is still being made today, but it is hard to get, and mostly around Christmas and Thanksgiving. It is also very expensive compared to dry yeast.
But every year folks drag aout Great-Grandma's hand written, roll recipe or something similar. And since it says in her handwriting to use 2 cakes of yeast, most folks go to the little neighborhood store that gets it in then and buys it. The last time I bought it the cost was over 2 dollars a cake.
Well being the curious type as well as cheap I called the 1-800 do you have questions about our yeast number. They nice folks said there is no differance between dry yeast or cake yeast in the final product. One package of dry yeast or 2 1/4 teaspoon of the bulk product will work fine.
The reason they still make the cake yeast is that Great-Grandma said to use it.
This is one place my cooking can be less than 100% historically correct, but it most likely saves me over a $100 a year. The last yeast I bought was bulk and I got two pounds for about $5. No hardcore has ever complained or even known the differance.