I can't say whether Devin's banter is better than JLB's. But in terms of stage presence, the reason why Devin's act is so much different has to do with the music he is playing. He wouldn't have so much more stage presence if he had to remember and play Count of Tuscany or the Alien.
If a Dream Theater show is like watching a top classical pianist try to play a 2 hour show of Chopin and Liszt, Devin is like watching Drake. Yeah, I mean, there is going to be a difference in how they interact with the audience from the stage.
Drake as in the rapper Drake?
Look, I'm the king of bad analogies and some of these even I wouldn't use.
As long as there's an "Iron Maiden" and a "Bruce Dickinson", I think the notion that only simpler music can support a dynamic stage presence is a faulty conclusion. We KNOW what DT is after 30 years. This is what we get. We KNOW what Devin is after how ever many years. That is what we get. Comparing the two is useless. It's not, at this point, whether they "CAN", it's whether they "WILL".
And if they don't, well, I think that's on the listener. I'd honestly be pretty bummed if the band was reading all this and going "wow, the fans said THIS, we have to do that!" I want what DT wants to give me, not the other way around. I know for me, and only me, while I accept that it isn't perfect, I've pretty much liked what I've gotten over the past 30 years (yes, I got on board with Images and Words back in the day).
I don't want to open a can of worms here, but "The Portnoy Incident" is a far bigger issue for me than James' singing. Sorry, it just is. (But even then, I'm STILL on board).