Hi BigEyeSleep.
Welcome to our Mattress Forum 
Sorry for the delayed reply. Please let me know how your mattress search has progressed since you first posted.
Generally we caution against trying to find comparable (or even build comparable) mattresses. A single difference in any component, even a .5" transition layer or the mattress encasement, can change the feel quite a lot. Rather, we (@phoenix and the rest of us forum moderators) recommend buying based on your PPP (pressure relief, posture and alignment, and personal preferences).
That said, let’s take a deeper look!
If we take a look at Magic Sleeper’s website, we actually see:
“Comfort Compares To: Beautyrest Black® C-Class 13.75" Firm Mattress”
That’s a good first sign. Do you know which Beautyrest firmness/loft you and your wife slept on?
We also have these details available to us:
Support System:
1055 Individually Wrapped Coil System
Foam Encased Perimeter Support System
Comfort Layers:
Cooling Technology Woven Into the Cover
Cool Surface Foam
Quilted Gel Memory Foam
Ultra Premium Gel Memory Foam
Comfort Layer with Alpaca, Cashmere and Silk Fibers
Pure Latex Foam
14" Total Mattress Height
Without having the foam densities for this (or the Beautyrest) it’s hard to make an exact comparison in terms of durability. If you’re able to locate those details, I’d be happy to make a further comparison. I’ll also look further myself.
The major similarities I see here are cooling technologies woven into the covers of both mattresses. Both mattresses are built with the intention of providing comfort and cooling, but the Magic Sleeper Black Oasis stands out a bit over the Beautyrest for its use of high-end natural fibers and latex foam (arguably one of the most durable mattress materials).
I’ll be giving a call to Magic Sleeper to ask for more details on their foam densities and will update accordingly. You may also wish to call to see how they arrived at this comparison, and if they have any additional recommendations for you.
I’ll be back 
NikkiTMU