Well, of course 175 gallon capacity is better than 125. You won't actually gain that much, but no matter how you set it up it is a significant increase and that's always a good thing.
A sump has far less plumbing that is pressurized; it's mostly gravity-fed, so much less likelihood of leaks.
How long does it take you to clean the mech media in a canister? How often do you typically do it?
In my biggest sump I can swap out the first stage of my mechanical filtration in under 60 seconds, taking my time and being careful not to spill a drop of water; I do it almost every day. I can swap out all the mechanical filtration in maybe 5 minutes.
I also want ease of access and maintenance.
And is why I "don't" stuff the sump, and its plumbing into a cramped cabinet below, where I'd need to contort, to wrangle with non-user friendly placed gear.
With an open surface area, everything is easy to access, just standing next to sump, and reaching in without bending
(an important facet for an old codger like me),
No O-rings, few moving parts, or cheap plastic pieces to lose, or to fall apart after 2 or 3 turns.
To emphasize my point, the thread below
Yesterday when I unscrewed all the white knobs one of them cracked and broke apart so that is a weak point. Turned on the filter and that's exactly where the leak is were that one knob is not tight. Would buying all new knobs be okay? Or is this leak something else?
www.monsterfishkeepers.com
And because I like "tall terrestrial" plants growing above the waters surface, the open area above, offers lots of room for that extended growth .
A slight down side , is predators have easy access to dine on the sumps resident shrimp, at their leisure.
But another up side is ease of water changes, to change 100 gallons or more, in a few moments, I add (friction fit) a length of PVC to the sump inflow, and instead of flowing to the sump, old water, (instead), goes to the garden.