I'm comparing them both with prediction. If you're able to do partial prediction with either, then I don't see a reason to do an RUD 2twist instead of OCLL.
Especially if you say the recognition time should be about the same for both, why not do the standard OCLL which is half the moves of the RUD 2twist.
I can't really tell from your response if you actually think the PLL recognition time (with or without prediction) is about the same, but I'm going to assume that's the case (correct me if I'm wrong though). Assuming that, you're disregarding a very important detail. I'll try to explain that and precisely when the RUD 2-twist has potentiaI.
First of all, let A, B and C be your average execution time of the OCLL, the 2-twist, and half of the 2-twist (including the U'), respectively. To make a fair comparison, the algorithms should be executed with about the same amount risk (instead of saying that the 2-twist is risky, just slow down the execution as much as you need). Also, let R be your average PLL recognition time (same for both methods), and P your average PLL execution time (also essentially the same).
Then, the average time tA it takes to solve LL with the OCLL is clearly tA = A + R + P. As for the 2-twist, there are two scenarious. In the first scenario, we finish recognition before the end of the OLL execution, in which case the average time tB1 it takes to solve LL is clearly just tB1 = B + P. In the second scenario, we finish recognition after the end of the OLL execution, and the average time tB2 it takes to solve LL then becomes tB2 = C + R + P (NOT B + R + P, as you're suggesting).
Now, since C is clearly smaller than A, it follows that tB2 < tA, proving that the 2-twist is always faster in the second scenario. As for the first scenario, it's pretty obvious that tB1 < tA precisely when B < A + R. In other words, the 2-twist is faster if its execution is faster than the execution of the OCLL and the PLL recognition time together. Since A is clearly smaller than B, this simply means that the OCLL can be faster if your PLL recognition is faster than (B - A). But if it's slower than that it's going to be worse, no matter how much slower it is, and no matter if you can finish PLL recognition before the end of the 2-twist or not (contrary to what you're suggesting).
I hope that cleared things up!