Choosing between alternative X axis bearings designs

[eci22]

Hi all,
Apologies if this has already been asked but I'm weighing up my design choices and wanted some input about the different arangment of x axis bearings. I don't know what or if these two designs have an official name (so i didn't know what to google) so I've called them alternative A/B

(The pros and cons are based on my limited understanding, so please correct me if I'm wrong)

Alternative A


Pros: easy to implement and calibrate how parallel the guide rails are, more travel than alternative B
Cons: Tool ends up being further away from the axis than with alternative B

Alternative B



Pros: Tools can can be held closer to the axis, better for rigidity
Cons, much harder to check how parallel the rails are, less travel than alternaive A

Most of the DIY machines I've seen use A, but it would be great to get the merits of each one.

About my build
Work area: 300x400x150mm, fixed gantry
Frame 50x50x3mm Mild steel
Spindle: Chinese 2.2KW water cooled
Intended cutting Materials 6082 Aluminium

Thank you