One zone ac/heat together or two zone 1 ac 1 heat?

[GG123]

Which is better and what reasons
1. One zone heat and ac together where the ac condenser is above the forced air furnance in the basement
versus
2. One zone forced air in the basement with its own duct and one zone ac sitting in the attic with a separate duct for ac.

The house is a split and currently the furnance is downstairs in the basement for whole house and the ac is outside with air handler in the attic and the ac has a separate duct work.

Thanks

[beenthere]

If its already installed like that. Its usually better to keep it like that.
Your heating ducts may not be large enough for A/C.