I'm going to do a bit more playing around over the weekend, but I finally started comparing my Deep 4 with the TB-10. I'll start a formal thread at some point (maybe not).
My Deep 4 was Rob's first, so it has the additional tone control knobs that later ones do not (stacked knobs closer, volume on the other one). The Takamine has a 3-band EQ and volume, as well as a built-in tuner. In addition to the EQ, it's got what they call "Cool Tube" technology which is essentially a tube-based preamp.
I need to the the TB-10 properly set up, but I did change the strings. I hated the roundwounds that were on there (no idea why they'd put those on it). It's now strung the same as my Deep 4 - the Rotosound RS88 set, but the bottom four of a 5-string set (75-100-115-135). Yes, that's probably unplayable for most, but such is life
I'm just playing them acoustically right now and doing feel comparisons, and when I go up to the rehearsal studio, I'll plug into my amp.
Feel-wise, the TB-10 is vastly different than the Deep 4. The Deep 4 plays like a bass guitar. The TB-10 does not, even playing it like one. The necks are so dissimilar. The TB-10's neck is about as close to an upright neck as you'll find. It's VERY thick. Now, my Deep 4 is based on my P neck which is a hunk of wood. The TB-10 puts it to shame. So if you prefer a smaller, less hunk of wood neck, you most likely will NOT like to play the TB-10. Switching between them is a lot like going from a full scale bass to a short scale bass. It's that different.
The neck profile is also different. The fingerboard on the Deep 4 is flat whereas the TB-10 has the rounded curve like an upright. You can't approach it as you would a bass guitar.
Playing them acoustically, the TB-10 is much, much louder but that's no surprise - it's got a larger chamber.
Weight-wise, it's also no comparison. The Deep 4 is MUCH lighter than the TB-10.
More as it comes ... this is going to be fun.