At a first pass, they're both great kit but IMHO pitched different levels.
Get right down into the specs, especially interoperability and connectivity with the aircraft systems, particukarly the A/P and FMS if you have one.
Thats where the the vipers live, and it is never never simple. You would have to consider a full review of the real retro cost against a new or later model aircraft with the same sort of gear before you race off and spend the money. A sows ear dressed in silk, with bling ear rings even, is still a sows ear.
