From DDMS
"An even better deal is with Marriott’s miles+nights packages. 90K Starpoints transfers into 270K Marriott Rewards points. That can be used for 157K United miles and 7 nights in a Marriott category 1-5 hotel with the 25K bonus miles from this United promotion."
"Alternatively about 83,333 Starpoints becomes 250K Marriott points which is enough for 135,000 United miles and 7 nights in a Marriott category 1-5 hotel with the 20K bonus miles from this United promotion. Even if you don’t use the 7 night hotel certificate being able to transfer 83,333 Starpoints into 135K United miles is an effective 56% transfer bonus!"
To clarify shouldn't the only difference between transferring 90k and 83333 be whether you fully utilize the 25K max? Yet the rate is different...?
157000/90000=1.74
135000/83333=1.62