I sell both the PSR740 and the Korg i35 keyboards. There are several differences and I will try to highlight the major ones.
The Korg has a 16 track song sequencer which allows for complete microscope editing. This allows you to change a single event of any type without having to use a computer sequencing program. The Korg also has a program editing function which allows for changing any sound in the keyboard via filters, envelopes, effects, etc. and store them in a user program bank. The i35 also has a guitar input and guitar effects such as distortion, chorus, flanger, etc. One of the nice features of the PSR 740 if you need it, is to record your own user styles and save them. On the Korg, you can only load user styles from disks produced by Korg or made on the Korg i30 keyboard. The Yamaha sequencer is not even close to the quality of the Korgs as far as how much editing and how easy it is to use and playback songs. Both have very good vocal harmonizers on board, but I think the edge goes to the Korg. I like how much easier it is to find the styles and sounds you want on the Yamaha because the Korg only has buttons to choose the style and sound you want and they are not labeled. The Yamaha has a catagory file page and lets you scroll through the sounds seing which one you will be going to next. I like the multi foot switch option with the FC5 pedal better on the Korg. Yamaha only lets you use one foot switch and one expression pedal, Korg has the five pedal FC5 plus one sustain pedal and a volume pedal. Both keyboards are outstanding for the price but the Korg costs a few hundred dollars more than the Yamaha. The sounds and styles are very different on both. I like the Korg intro's and endings and their styles better than the Yamaha's , but some of the sounds I like better on the Yamaha, such as the Yamaha Acoustic Piano and electric pianos. Brass and guitars are very good on both. In my opinion you can't go wrong with either one of these. If you have any more specific questions, let me know.
Kaye's Music Scene