10 times the power of Hubble!!! But i still bet for Hubble. The problem with hubble is that it cannot be easily upgraded and the parts can only by really high first very first class parts. Because if it fails then... you cannot just call the technician to pay a visit.
The advantage of Hubble on the other hand is that 100% of its power is used to observer. This does not happen with the other scopes that will need to overcome earths atmosphere. And sometimes, some very small stars just will get lost because of the atmosphere...