The comparison was made with regard to them both being Middlesbrough to Whitby services.
I actually pointed out the differences between two in my post - with the X4/4 'going around the houses'.

The majority of those travelling between Boro and Whitby will use the X93.
However, apart from the odd location, like Guisbrough, it isn't going to pick up the additional custom en-route, to make a difference to its revenue.
You can even say the X93 has the 5 as competition between Boro and Guisbrough, so loads are diluted between those services.

With the X4 going around the doors, it has local and longer distance fares. Unlike the X93, it passes through enough settlements to pick up additional passengers.

This additional custom has lead (whenever I have used it or the X3) to standing loads.
Appreciate it won't be like that all the time and I don't profess to be a regular.

However, what you said about the year round custom on the X4, adds weight to my point about the X93.
It needs to increase revenue if it is ever going to see the investment in new vehicles.
How does it do that, without the journey time increasing in order to attract a larger market?