If you look into the manuals under "Latency and Monitoring" then you can see in the tabular, that the pure converter latency for AD and DA are very low and also the same for both recording interfaces.

Whats different is the circuit around and that the interfaces are using different drivers, where the MADIface driver is the "more modern" driver which allows smaller values for ASIO buffer size (32 vs 48).

But this makes not that big difference. For pure recording this doesn't matter much, its more interesting for people working with VSTi's.

You can see here in the tabular the different round trip times of different RME products as reported by the ASIO driver to the DAW. The 802 is compareable to the values of the old UFX and the UFX II is compareable with the values for UFX+:

Another advantage of using the MADIface driver is, that recent new interfaces also use this driver:
Digiface USB, MADIface USB, MADIface Pro, MADIface XT, UFX II/+, ADI-2 Pro/DAC

So you can connect / combine several of these interfaces and access them directly from DAW by loading the ONE ASIO driver. You only need to synchronize the interfaces. The amount of interfaces and channels still depends on the capabilities / performance / DPC latency of your PC as usual.

By this you can i.e. get an UFX II/+ and nicely integrate an ADI-2 Pro into the concept
AND directly access all devices from DAW without having to perform routing on the UFX II towards ADI-2 Pro.
You only need to take care, that the devices are clock synched and use the same ASIO buffersize.