Let's see, not sure where to start or end but here's some thoughts.
I love the U5 and the redid, I've owned both.
I'll say what I like about them that I think, imho, makes them unique and separate's them from this SamAmp pre.
Here's some overarching thoughts I have about them.
This pre is not a DI like the u5 or reddi but a pre, and awesome one at that
The reddi and u5 are "standards" and are easier to find resources about - i.e. troubleshooting tone and various other sonic artifacts.
For example, a foh engineer or studio engineer could be stoked that you've brought a u5 or reddi to your gig/session, while they may be indifferent to the SamAmp.
-Lot's of more tone features than the reddi, not as much tone shaping or extreme tone shaping abilities as the SamAmp.
-Love the tone out of the U5
-Only a few more functional features than the reddi.
-Lots of people define the u5 as "sterile", I find that term lacking, I think of the sound that it does do, as sonically enhancing and a very musical sterile. Awesomeness!!
-The SamAmp will, hands-down, out perform the u5 in sonic variety.
-lots of people talk about the "gooey, tubey, and that sound" they get from the reddi -- which is true
-However, I think the magic comes in the higher frequencies and higher up on the fret board. It actually sounds like a really awesome tube amp being mic'ed. I notice it the most in higher frequencies. The u5 and other standard pre's all sound great in the high end, buttttt, the way an amp allows a bass's higher end to still have a girth and low-end presence is what the reddi does, and it's the only pre i've found to do it so well.
-Not much tonal variety, you can turn the gain up, but the tube break up is minimal at best and can often be too hot of a signal for the foh or studio wo a pad.
-The lowend that people talk about IS yummy, but not exclusive to the reddi, imo. I believe a low end bump for other pre's can match what the reddi does, in the low end.
-Huge tonal palette
-All the way from a barely noticeable tube/vibey color to an all out fuzzy, pleasant distortion/od. Just to clarify, when I say distortion, I don't mean anything like some crappy digital distortion.
-The EQ: this is a pretty cool - with this box you have Tube-EQ. Instead of it being a post-tube thing -like some other amps or pre's - bumping just the eq can add tons of color and tube flavor to the signal.
SamAmp input/output jank:
-You may have notice that there are "three inputs".
Input 1 has the greatest flexibility since it runs the signal through every feature (eq, tone switch, etc) including the gain. The most fun input.
-The Input 2 is the most "reddi-y" signal. It is the bass running through the the gain tube and not the eq or tone path.
-The Input 3 is the most uncolored tone and is good for a/b'ing tones.
-The Outputs - this is the coolest part to me. Yes, you can run one output with it's own level control to your amp and the other to your foh/daw, makes so much sense, i don't know why more companies have parallel outs with their own levels.
** By far my FAVORITE feature is taking one output and running it through the dirtiest fuzz,od,distortion, pedals I have and sending it to my daw or di and then taking the "clean", second output and running it straight to my daw/di as well. Then using the level controls, for each respective output, and blending it to taste!! (merge function on radial's di's is awesome for this)
-Yes it is much less cash than the u5 or the reddi.
-The SamAmp cannot mimic the u5.
-The u5 can't mimic the SamAmp
-the reddi does sound awesome.
-The u5 is awesome too.
-Since the SamAmp comes from a builder and since it is a one-off it will be harder to flip on tb.
-I love the form factor, little silver looking box.