Please explain - crab compost vs worm castings vs compost

Last year I repotted some of my amaryllis with a bit of "blue crab compost" and they thrived. It was the best improvement I've made in some time to those bulbs. This year, I didn't find crab locally, but do see worm castings and a packaged product just called "compost." The "compost" product looks more like plant matter, and in no way comparable to the crab or worm products, and I suspect that there will be a difference in effect. Can anyone enlighten me? I don't have the facilities to produce compost, so that's out. I'm trying to decide whether I should go out of my way to find the crab product, or use something else. Thanks for any advice.

I am not familar with crab compost but worm castings are good.
I have three worm bins and I produce 15 or 20 gallons of worm castings/compost a year. I mix mine with my purchased planter mix.
A lot of counties have composting plants where the public can get compost for free or a very small cost. Check around.
George

Thanks for the tip. I will check with the county.