You win some reliability since you up the rpms through the drive. Prop shaft rotates about 10% faster and increased rpms on the prop shaft can in most cases take a bit more HP and torque. The prop pitch goes down and the abuse from the prop is a bit lower as well.

BUT - what is the differences in top speed, handling, cruise etc?

I feel I lost around 2 mph up top. Unfortunately I had just finished final tuning of the EFI when I lost a 1.36 drive. The next time I ran the boat it was with 1.50 drives.

It's a loaded question that depends on the setup you are running. Gearsets multiply torque. The deeper the ratio, the greater the torque multiplication. Shallow ratio (1.36) drives usually do better at top speed because they can use lower pitch props, which are more efficient. Steep ratio drives may do better at lower speeds where you can effectively multiply maximum engine torque. Cruise is up for grabs based on your engine's power and torque curves.

Anyone building a reliable long stroke 8000 rpm engine making peak torque between 3000 and 6000 rpm please give me a call. I'll take some 1.75 ratio drives!