I agree. I love my Tube gear. To my ears, the PF-50T is the winner. It's as simple and bare bones as it can be. I literally just have the bass boosted a bit and everything else is set flat. As expected, it has that Ampeg sound that I personally love. But really it's not a fair comparison as it's like comparing a bazooka to a pistol. It's not a "preamp" and it's not a pedal.
The great thing about the digital rig is it's use on a live gig. It's not as susceptible to EMI interference as it's all digital. You can switch tones at the click of a switch. Acoustic or SVT for a rock song, B15 for a Motown tune, Bassman amp is in there too. Then you can have different compressors, drives, and such for each patch...and you have 4 snapshots for each patch so you can change your tone on the fly mid song.
The Alpha is really good and for how simple it is with so little tone shaping choices, it works far better than I expected it to. I tried various combinations of the switches and I liked the left switch in the "Deep" setting and the right switch flat. I also liked the "Dark" and "Bright" setting which gives a bit of a scoop. It is really more of a colored DI type device than a true preamp/DI. But it sounds so good you could use it all by itself for recording or on a gig.
The Shaw sounds great too, has a more flexible EQ, a 9v output for pedals, and is just more flexible all around...but it's physically HUGE. It's all hand wired with no PC boards inside, so it's big for a reason. I also put a NOS JAN tube from 1945 in it. JAN tubes are "Joint Army Navy" so it's a little piece of WWII history.
The Pro DI was just a DI...so I didn't expect much and it delivered about what I expected. The channel strip on the mixer sounded better than I anticipated, but it really shows just how dry solid state stuff is. No character.