[Physicist]

Does Hubble's different perspective help, and would a deep space probe be enough better to justify its cost?

They don't use Hubble for tracking asteroids, and I'm not sure it could do a far better job than a smaller, ground-based telescope. The first order of business is to find the darn things, and for that you need more eyes rather than better eyes.

I'm just guessing here, but I expect that the biggest advantage to a space-based telescope would be to give you a long baseline for parallax measurements. If that's right, the goal would be to get the space-based telescope as far away from Earth as possible. Perhaps a Moon-based telescope would be a good solution.

[conservatism_IS_compassion]

the biggest advantage to a space-based telescope would be to give you a long baseline for parallax measurements

. . . which would seem to argue for getting a telescope into deep space to get some serious parallax. Possibly a Pluto-type solar orbit?