nch,
Glenns that are a little less ripe will probably not taste any better. For Glenns, my observation is that you cannot let them get overripe or else they will taste sour/fermented .
Yes, I agree, the Glenns are sweet, but not very complex. However, they are very easy to grow and the tree is not bothered by colder winter weather in Orange County.
I now have 20 varieties of mango trees, most very young...so I have not fruited most of them. However, from visiting Hawaii and attending taste testings, my favorites are white pirie, lemon zest, coconut cream, alphonso, and kesar.....these have complexity to them. White Pirie, Alphonso, and Kesar have a noticable perfumy floral scent and flavor. Lemon zest has a rich orangey flavor. Coconut cream is a fairly new mango (Gary x Edwards) and is just wonderful overall, creamy and flavorful.
btw, cukes is a term for a tiny mutant "seedless" avocado...So I was drawing a parallel to this.
I've never seen the small egg-size mangos that you are referring to...I assume they are in Asian markets. Perhaps just small manilas.