In my opinion, the most important things for a bot to do in order are:
- Intake cubes
- Make new stacks
- Score and descore towers
- Add to existing stacks
Most of the match will be spent intaking cubes, so you’ll want bots that can do that quickly. For this, side spinner intakes are pretty much a necessity. Top-down intakes, like you’d find on a tube lift, aren’t going to be as fast. Trays win in this situation, especially those with more powerful 2-motor intakes.
Making new stacks is the next most important part, and ideally you wouldn’t have to lift your intake/cube holder up over the deposited stack (for the sake of speed). Because of this, trays win here too.
Scoring and descoring towers is a tricky one. Here, the simple tray is at a definite disadvantage, as it can only score by letting cubes fall out the back of the tray into a tower. Cube tubes, complex trays, and tray lifts are pretty even here though.
Finally, scoring on existing stacks. This isn’t as important as the rest, as with good planning, this shouldn’t be needed very much if at all. However, the tray lift and cube tube are probably about even here if you account for the time taken to line up. It’d be hard to line up the tray stacker well.
Overall, the tray lift is just as good as an average tray (with the notable difference of having a less powerful 1-motor intake) at stacking, and just as good as a cube tube at placing or descoring from towers.
I think the idea of two specialized bots on an alliance is interesting, but not very practical. Two well-designed tray lifts can be just as efficient at stacking as a complex tray and just as efficient at towers as a cube tube. With two identical robots, each one can stay in its own corner of the field for stacking and towers, reducing the time spend driving around the field. It also makes an alliance less susceptible to pinning, as the unpinned robot can do both jobs (towers and stacking).
For the sake of argument, let’s look at some potential motor breakdowns:
1m Intake Pivot
1m Tray Pivot
The tray on a tray-lift will be almost identical to a complex tray (with the obvious 1m intake caveat, but I don’t think that will pose a huge problem assuming the tray is slippery enough).
The lift will be 2-motor, just like on a cube tube. So it will be just as fast.
I honestly don’t see what is keeping the tray-lift from being just as powerful as the other designs at their respective strengths. It’s the best of both worlds in my opinion.