After doing a bit of reading it seems as though any loss of nutritional value through freeze drying is minuscule. So it would basically come down to what you and your fish prefer.
Freeze dried bloodworms should be rehydrated in a cup of tank water before being fed to your fish to reduce any chances of gastrointestinal problems. I've read that the dust from freeze dried fish foods can cause respiratory problems, so just do your best not to snort the leftovers and you should be fine. Freeze dried seems to be the less expensive way to feed bloodworms for the most part.
Frozen bloodworms are every single one of my fishes' favorite foods. They just go crazy over them. Frozen are definitely more expensive but as long as my fish enjoy them and I have the extra money to spend, I don't mind shelling out a few extra bucks.
I did read that bloodworms in any form can cause allergic reactions (such as itching, burning skin and hives.) Some believe that these reactions are increased over time. I've personally never had any problems with them (so far) but I always wash my hands and arms thoroughly after doing anything fish related. Some advise to just wear rubber gloves as a precaution.
And that's what I learned about bloodworms today.
Wow thank you for such an in depth response! On behalf of my fish and I, thanks!
I highly recommend the use of gloves for feeding blood worms. I can feed them but if I forget to wash my hands right away, I know my eyes are going to swell shut.
When I feed freeze dried bloodworms, I use a clothespin on my nose so that I don't inhale any when I am handling. They give me rashes and cause me to itch.
My fish don't appear to enjoy one type over the other, and freeze-dried are much cheaper.