The internal on our 850 was slow to connect on deck under the Bimini and solar farm. I added a cheap magnetic base antenna designed for truckers to slap on the roof. It is internal to the fiberglass instrument box on deck. It works well.
The Vesper SP-160 is a very good powered splitter with no performance loss. Vesper also have an antenna tuned between AIS and VHF. I have installed XB-8000's, the splitters and Vesper AIS/VHF antennas on two different boats and used for ten years with zero problems ever. Using a splitter allows one antenna at top of the mast to have long range VHF AND AIStransmission.
The 8000 has an internal. But if you plug in and mount the external (which comes in the box anyways). Right beside the ais underdeck it will be much better. You don’t have to Actully out the external antenna outside.
I would take the 8000 Abd normal vhf over the cortex