I would have thought it balanced out. For example (hope this makes sense), when Steem is up the value of votes is also up, so a vote that would be worth $1 now, might have been worth $2. Effectively that means although the conversion rate works out higher per dollar at the low end, you would have been getting it on $2 not one at the higher end, which would still have yielded exactly the same value. However, higher voting value gives more on the SBD conversion side, which can be changed to SP at a higher rate giving a bigger boost to your SP if you choose to take that route.