They are very different games. I play with pretty much everyday to PSOBB on Ephinea. I tried and PSO2 Meseta played a couple of hours to PSO2 on the JP server years back. These makes it so you're not running around looking for X Tech or Y weapon to deal with the circumstance and give combat a better sense. Music and the aesthetics of PSOBB are a few of my favorites in almost any sport. The art style for everything was on point although it's likely nostalgia. PSO2 takes inspiration from the sci-fi dream feel but it's fairly derivative and uninspired imo.
If you've played with the MH series (which in case you have not you should, the series was inspired by PSO and was Sony's Capcom's response to the online activity genre), It is like the way MH4 and MHW compare. MH4 has a pace that is more deliberate and slower. MHW has a pace that is quicker and action. Neither are bad, just different experiences. It's absolutely free to play so give it a shot. Just don't expect the PSO void to meet with. I really don't think I'll ever stop playing PSOBB even with PSO2 due to their differences.Great analogy with an MH4 vs MHW comparing to PSO vs PSO2. The two very good matches, both FEEL like they belong in precisely the match collection that is same, only in a really distinct ways.
I'll speak into PSOBB myself back into the 17, as someone who logged many hours. As has been stated, PSO2 is far quicker paced than the original PSO. Phantasy Star Online 2 itself feels very different. It caters to a newer audience. The biggest factor for me is you'll go through assignments. I haven't taken longer than 35 minutes to finish any one mission, and that includes the current end game material on NA. To put it in a way that you can probably relate to, no mission I have done thus far has felt just like a full incident 4 desert run on Ultimate or a Central Control Tower operate in episode 2 (I am certain you know exactly what I mean).
Another major shift is that it's not so much about maxing stats (though this remains significant ), but it is about correctly constructing your skill tree to the end game as YOU want to play. With the accession of a main and sub class mix forcing your construct, there are a number of ways to buy Phantasy Star Online 2 Meseta create each class effectively (in some instances, more than 1 way is end game viable). Min/maxing stats just isn't as important, which I like better. All in all, I say go for it. I've already put in countless hours into PSO2 and I do not plan on quitting anytime soon.