I haven't experienced a Grand Central 180, but the Hull trains ones were pretty dire, always breaking down and a rough ride, even water leaks in heavy rain on one journey back to Hull a couple of years ago. The question is what are Grand Central doing differently to get the 180's to work. I agree with others, we are lucky that GC survived the pandemic, and GC would not be looking to spend money. GC are now the only operator using diesel traction into King X regularly, and this has been discussed here
https://www.railforums.co.uk/thread...ting-at-trainshed-subsurface-stations.223463/ I have seen the GC Bradford service at Doncaster, and it never looks particularly busy, although the Sunderland one at York seems busier (just a look through the windows as the trains leaves/depart).
Bearing in mind that as far as I can see once off the wires neither GC service will exceed 75mph would a 5 car 80x with 2 engines be practical or cheaper to run/lease.
In terms of passenger comfort LNER 80x 2nd class is not comfortable, particularly in the airline seats. Hull trains 1st class is comfortable, and well worth the extra money for a Hull trains 1st advance fare. I think the configuaration of the carriage makes all the difference, if GC bought 80x maybe they would go for a better 2nd class layout in order to differentiate themselves from LNER at the expense of a small amount of capacity.