My wife and I were faced with a fairly similar decision when we were weighing the money vs. size vs. age vs. condition of a Maramu and a Mango and a Super Maramu.
Between the three there was over $100k difference in pricing so we just studied and studied and visited and made estimates of refit and operating costs and it seemed to never get any simpler.
Finally we decided on the super Maramu and I can truly say I think we made the right call. Each if the boats had it's merits and detractors but after our first year in the SM it became apparent that we did the best ~for us~.
I totally agree with all the posters who say that it's be hard to give up this boat for another, regardless up up/down scale and comparative factors because we are so heavily invested in having learned, tweaked, adjusted and discovered all the ups and downs of the boat we have.
My only comparison has been to sit and share time 54 owners. Of course it's natural to compare notes and that's pretty much the end of objectivity right there. One 54 owner Bates the flush-top deck lockers lockers because they leak. Mine are raised and don't leak .. but the reason they went to flush is because you can trip on them.
I love out handhold-to-handhold movement below deck. On another (older) SM my wife nearly took a fall on the companionway reaching for an expected handhold that hadn't been invented yet on that boat.
The 54's hard top is a great advantage .. unless you like flipping the canvas down for the air.
And yes, I'd love the extra speed, extra foresail, different stateroom layout and newer gadgetry on a 54, but I'm also really happy with what I am familiar with; and from what I hear, a smidge less.comexity and easier access to some mechanicals on the SM.
It's just got to come down to your evaluation of wants and needs. I've done a fair amount of single handing on a Super Maramu and it's easy enough. The 54 I conceptually the same so I can't see how it's be any different. Crew accommodation is excellent on both, maybe the 54 has an edge with more hatches when it's miserably calm somewhere, but then .. more chances for leaky gaskets. You see what I'm driving at :)
Hope you have a great "hunt" and eventually find the "one" that fits best.
SM 209, Adagio
Deltaville, VA USA