The second way I think would give you less bonus as the higher you get on the first way, the higher the House Edge you get back.
Bet 100k 10x would get you 2,000 bits while the first way you will have reached 1 million bits bet and have got 200 bits + 2,500 bits so it would be 700 bits better.
I see. However, first option will only be good on a short term basis, second option is for long term because that will give bettors continuous profit even after reaching a 100m bits total wager.
Anyway, good luck on your sweeper game. We really need to think a good way to promote our sweeper game (I manage a sweeper game too)