1:2:4 mix or 1:3:3 mix

1. M25(1:1:2)

2. M20( 1:1.5:3)

3 M15 ( 1:2:4)

But as you say about 1;3;3 In this mix sand contents are more and this mix is OVER SANDED and as much sand than requirement reduce the strength. Generally contractor use over sanded for easy finish.