When I got into SB, I was between Feel Euphoria and Octane, so Neal had already left, but I started getting into the band with the Neal-era albums (after discovering Transatlantic by way of Mike Portnoy, which I'm sure many of us here did as well). Since the band were already 2 albums deep with Nick as the vocalist by the time I was getting into them, I really dug how the band's sound evolved and enjoyed both eras of the band. Octane remains a favorite to this day because of that, as is X. It really threw me for a loop when Nick decided to leave the band, and I had never heard of his vocal replacement before, but when BNADS came out, I was blown away once more.
I think each vocalist of SB has their own charms, and I would agree with the assessment here that Neal has a very powerful every-man voice that makes his music so easy and fun to sing-along to. Nick has more power in his upper range, and does some fun stuff with his vocals over his four albums fronting the band. There's a lot of energy in his vocals that I quite enjoy (though I can't say I sing along to the NDV-era stuff as much as the Neal-era songs). And Ted can feel like a solid mix of both Nick and Neal, while adding some unique flavors of his own. In recent years, I've also dived into Enchant, which has helped me appreciate the evolution of Ted's voice, fronting a band that was more like Rush, then moving on to SB (which is more like Genesis/Yes at times, though they've certainly carved out their own sound over the last 25 years).
I think watching the Snow Live concert really helped me appreciate all three just about the same, though I will always leave more room in my musical heart for Neal's music (not that I don't like what Nick and Ted do, both with SB and in their other projects). It was certainly a treat to see and hear all three frontmen together on stage, performing my favorite SB album of all time, taking the lead in different songs and parts of songs, and even letting Jimmy sing lead on one song! I think because SB was kind of built on vocal harmonies and interplay, that they could probably change lead vocalists again and I might not be so shocked, just as long as they continue to write great vocal melodies and harmonies.
-Marc.