I didn't watch the vid. But I have owned a lot of V30s. '80s and early '90s T3904. '93/94 Mesa spec T4416. '90-'00 Marshall spec T3897. Late '90s T3904. Modern T3904A, T3897B, and T4416B.
From a visual perspective, there is one primary difference between the T3904/T3897 and the T4416: the T4416 back plate (the silver disk over the back of the black magnet) is smaller and has marks from machining. The T3904/T3897 backplate is larger and obviously cast (maybe they all start cast and are machined down for the T4416).
Over the years, changes have happened to all three. The earlier ones all have heavy doping around the dust cap (looks like a liquid stain around the dust cap). By the mid '90s this was becoming less common, and now you don't see it at all.
The cone changed. The ribs use to be very pronounced and narrow. They seem to have become less distinct over the years and some time in the early 2000s they changed to become very wide.
The magnet shrank. The thickness is the same, but it's now a few millimeters smaller diameter. It's most obvious on the new T3904, where now the magnet just barely peaks out past the back plate.
Sound wise, I have such a small sample size it's hard to say. The '89 T3904s are scooped and very aggressive. Similar to the '90-'00 T3897s. The '91 T3904s have a more relaxed top end but have a more obvious high mid peak. The Mesa T4416s are smoother like the '91 T4416 but don't seem to have that obvious mid peak.
The newer versions with the A and B added to the model number just don't sound the same. Not sure if it's the break in or the construction differences. They have more treble/presence and crispness to the tone.
