My 1st 4-strk was a YS. A .91FZ to be exact. I think you will be fine buying a YS as your first 4-strk. If you live in a high elevation area, the YS is better. I own Saito and OS engines also, so I can personally speak for them all motors. They all are great. Saitos and OS are less complicated to tune, but the YS is a true power house. I just ordered A YS 1.10 for my Funtana S 90. If you budget will allow you to buy a YS then go YS, but if your pocket isn't too deep a Saito or OS will do fine. It really all depends on what type of flying you are trying to accomplish and with what type of plane. General flying and over powering a 40 or 60 size plane, the Saito and OS are great. For acrobatic 40 to 120 size planes (3D especially), the YS is a better choice IMO. More power to pull these planes around and out of risky situations, plus the fuel tank can be mounted over the CG. The YS engines have a type of supercharger pump that will pull the fuel to the motor. Saito and OS can both do this if you add a optional external pump which cost more money and has to be mounted, so just get a YS from the start.

The Saito is lighter and cheaper than the YS and OS, but the YS is heavier, stronger and more expensive than both. Did I mention it is stronger than both? The weight difference is no problem for the YS. It will only affect your CG which can be corrected easily.

The Saito does have a longer warranty. Each motor has it's pro's and con's, but dollar for dollar, the YS is a better deal, but it does cost more. Some people only buy Saito, some only buy OS and some only buy YS. They have their reasons. I have tried them all and would say the YS is #1 because it is the strongest, Saito #2 because of it's weight, OS #3 because it is heavier than the Saito but has the same power as the OS.

I guarantee, if you decide to buy a YS, you will buy another one for another plane. That is a proven fact. The power and sound are very exclusive to that motor. Like the sound of a Harley is known when you hear it.