Hmm... It depends on what your preferences are. It doesn't matter whether you choose a classic or speedy challenge, the amount of money you can choose on your own but there are some differences, in a classic challenge there are first minimum plans consisting of 5000$ and 10000$, on the other had in a speedy challenge the first two minimum plans starts from 10000$ and 20000$. Of course, you can get more money by choosing a speedy challenge but you also need to pay more fees.

As far as I know if you opt for speedy challenge minimum account size you can get is $10k, while during classic challenge, you can choose $5k account.
These are all differences in terms of pre-funded accounts depending on the type of the challenge.
So, make sure you are ready to get into account management and act!
Also read their terms and conditions, it's important to understand all details.