benefits of $340
It is also interesting to have an answer for the game w/o surrender (easier case).
Actually if we could show that $340 benefits over 1% (regardless how much more) then we shall proof that $340 is a better bet than $430.
Here are the situations where $340 can possibly benefit over $430 (no Surrender game): BR2 pushes vs. BR1 loses
BR2 has 17, dealer has 7, BR1 less than 17
BR2 18, dealer 8, BR1 less than 18
BR2 19, dealer 9, BR1 less than 19
BR2 20, dealer T, BR1 less than 20
Please notice that with SR option available, after BR2 Stands, BR1 should SR (exept for BR2 20, Dealer T, BR1 19 - Stand).
Let's consider first (BR2 20, dealer T, BR1 less than 20).
In this case dealer has to make 20 and BR1 doesn't have to make 20 or 21.
We have ~ 10%*28*85%*37%*85% = .75%
Here is the brake down:
10% - BR2 has 20
28% - Dealer has T up, but not a BJ
85% - BR1 initially doesn't have 20 or BJ
37% - dealer makes 20
85% - BR1 doesn't make 20 or 21 (assuming dealer's algorithm for BR1 which is very close to "how to avoid 19% swing".
The other three give us ~ .1%
Now we have a really close call. We have to consider extras: when BR2 has any hand of 17 or more against dealer's other (than considered) cards vs BR1's worse hand. And assume push vs lose. It is actually more than .15 (proof is available). So finally $340 is slightly better than $430.
This last group is mainly the one which should be considered in Sr game as a possible benefit for $340, and this is less than 1%. So I think there is no need for total (global) sorting out. Looks like in Sr game $430 is better than $340.