Hi Totalee welcome to the felting world.
there's quite a difference between corriedale and merino.
Merino has a smaller shorter staple..as in shorter and much finer hairs.
Corriedale has fairly fine yet long hairs- but not as fine as merino.. if that makes sense..haha.
'They' say (whoever 'they' are..
) merino should/could be used for things that are against the skin- when wet/needle felted, it is similar to cashmere or pashmina in softness. Merino can also be felted in a very thin layer and is the choice for doing felting projects like nuno or scarves, etc.
On the other hand-I just finished a 1lb. bag of white corriedale and really like the diversity you can have with it. it is still pretty soft and can be used for all sort of things. as well it holds up on bigger projects like rugs, and vessels...
I also found corriedale easier to dye with kool-aid compared to merino- merino felts FAST!!! as it's so fine.
Another thing i also consider is price: 1 lb. corriedale is $14-16 CDN and 1 lb. merino is $20+ CDN where I am..although i plan on investing in lots of new dyed merino soon i hope!!
Anyways hope the info helped. HAVE LOTSA FUN ! Its all about the experimentation around here.