High-level descriptions of each:
Solinco - More or less the pioneer of a cheaper, better co-poly, with longer-lasting playability and grip/spin assistance geared specifically toward the junior and scholastic level. They beat the big, slow OEMs to the punch, and many still haven't caught up even after all these years. And huge props for also leading the way with gauge range -- most of their strings are made at every gauge from 1.15 to 1.30 (some at 1.10 and even 1.05!), which speaks volume about their confidence (and financial capability). I don't see Solinco or their mainstay strings disappearing any time soon.
Tru Pro (formely Tier One Sports) - A micro-variation of Solinco, minus the market presence, and a certain inevitable amount of "me too" in the product, with a somewhat-plasticky feel (typical of most stuff coming out of Taiwan), but with some actual innovation in certain ways. Black Knight was their first real splash, but DuraFluxx, Firewire, Tour Status and now Atomos (made by a new OEM in Germany -- good move) have certain merits. Similar to Solinco, they also have to be praised for offering at least 3 gauges, often 4, in all strings. IMHO, the re-brand has been the biggest setback to what little momentum they were able to build in what is now a very saturated market, but we'll see how they get on. I see them making it, but never having the recognition of Solinco, much less the big OEMs.
Grapplesnake - Their main value is their chemistry: co-poly formulations that feel like the "next evolution", starting with Tour Sniper, really accelerating with Tour M8 (a string that is totally unique in its feel) and I'd have no doubt again with Paradox Pro. They're actually doing something different in the R&D lab, and you can feel it in the string bed. That being said, they're a bit light on gauge range, and they lack a go-to smooth, round poly in the line, but I see them remedying that, partially with Paradox Pro, and I'm sure with more soon to follow. Above all else, though, they're certainly not just another me-too product, and for that, I salute them.
As for what's worth trying if you're wondering how different can the strings really be, I would go straight to Tour M8 for starters (probably 1.25 for your WhiteOut 18x20 XTD), then Game Changer (brace yourself for the bite), then try Atomos (string it low-ish to avoid the seemingly necessary "break in" session). Between those three, you're bound to have a "woah!" moment, compared to what you're used to with TB/Conf/H-G.
Hope that helps give some perspective.