I can tell you that the reels will be different. I have a Shield 5000. I watched the Joe O video and the size in the 6000 is concurrent with the Tsunami sizing trend. There currently is no bailless kit for the 4000, that I know of. The bailless kit I run on my 5000 requires that I extend my finger further and higher, since the spool is narrower and taller (as is the carriage).
My VS150 is more compact, and more squat, making it a good bit easier and more intuitive to manage the line.
I freaking love my Shield and I have absolutely pounded it to death without it skipping a beat. BUT it is not the same reel and doesn't handle the same way. Just an FYI.
There's a good chance I pick one up too, in the 4000 size.
ALSO, asked Joe the weight on the 6000. He responded with 19.3 ounces, filled. That is a bit of a load.