You have to pick:

I laughed out loud for a whole minute at the mere thought of having the excrete a crab.

THIS WOULD BE AWESOME.

Perhaps. Becoming a unicorn would give you magical powers and becoming a pegasus would give you flight. But an earth pony? All they get is pity. ;)

Either way, you'll be a freak (seeing as talking colorful ponies are not normal in real life). The unicorn might be worth it. The pegasus I'm a bit more dubious. Earth pony - that would suck.

So you're taking a risk.

Whole or like in pieces because i excrete crab all the time if the latter is true

Whole.