Don't judge other mahogany instruments by the one you have (you described it earlier as a "local" so I'm guessing it's an inexpensive "starter" uke). It is probably laminated and even if solid, it is probably way overbuilt (not to mention the playability issues you describe with the frets and such).
The bottom line is that any of the Mainland sopranos are good instruments with great "bang for the buck." However, each is different. My Mainland mahogany soprano is my best uke (and I own a KoAloha longneck soprano and have owned a KoAloha concert, so that's saying something). The mahogany is warm and punchy without being "brittle." I suspect that this is a case of the uke being a "pick of the litter" because, while all of my Mainland ukes have been great value for the money, this is the only one that I consider the equal of a far more expensive Hawaiian uke. It is as loud as my KoAloha longneck soprano and intonates better.
My Mainland mango soprano is an entirely different animal - bright enough that I use Ko'Olau Gold strings to take a bit of the edge off but still very punchy and nice with very good intonation. I've not owned a cedar soprano but I did have a Mainland tenor in rosewood/red cedar. It was a very good uke, played well and very loud, but it is the only Mainland I've owned and don't own any more. I just couldn't warm to the sound of cedar on a ukulele so I gave it to a grandson.
Finally, keep in mind that once you have a good uke you may want to experiment with strings as they can make a huge difference in the character of the sound. I have around a half-dozen or so different strings that I've found I like and I try each of them on a new uke until I find what works best with that particular uke. For example, my mahogany soprano has very heavy clear fluorocarbon strings, my mango soprano gets concert size Ko'Olau gold strings, my KoAloha longneck soprano gets tenor Ko'Olau Alohi strings, and so on.
John