I haven't been able to find anywhere online that claims freeze dried bloodworms lack more nutrient then frozen bloodworms.
Infact I have read the opposite about freeze dried foods...
http://www.shelfreliance.com/c/unive...t-freeze-dried
http://www.ehow.com/facts_5993868_nu...ing-foods.html
I am not an "expert", though...
However, I have personally had issues with freeze dried bloodworms making my one betta constipated...because they are lacking moisture, I believe they will expand in the belly and cause constipation on sensitive fish.If you can get frozen bloodworms, those would be better...plus it's fun to watch the bettas chase the worm..

I have tweezers I use to feed them. A variety of foods are best to feed in my opinion...
I feed a good quality pellet formula (new life spectrum), frozen bloodworms,and brine shrimp on rotation..not all at once.
If you live somewhere where there are mosquitoes you can also feed mosquito larvae...I personally haven't tried the mosquito larvae on my fish yet though.