Hello, I'm wondering about this too. The base prize is currently 18 satoshi, so if we take the highest Free BTC bonus (they are all proportional, it doesn't matter which one you redeem) that's 3200 RP for 10x bonus. 18*10*18=3240, so if you do 18 free rolls in a day (quite a lot, you have to sleep 7 hours max, if you aren't a robot then 6 or 5) you are getting 40 satoshi more than what you would get by encashing the points.
Keep in mind that to break even with Bonus Reward Points you just have to do 12 rolls.
Currently, i'm doing Free BTC bonuses because even if I get the same as encashing (or a little bit less) it's instant and the satoshi I make there gives me interest every day. But if the base prize goes down more I think it'll be worth more to encash them. (15*10*22=3300, I'm sure none of us does 22 free rolls constantly each day). Unless of course they lower the satoshi value of each RP.