I have owned the PS-4300 and I think it is a great, reliable turntable that is close to the contemporary Technics SL-1300, although I liked the arm and auto mechanisme of the Technics more and I also preferred the looks.
The PS-X5 is a successor of the PS-4300. They are basically the same turntables with fully automatic functions, virtually the same SBMC made base, motor, arm geometry, and the same specifications. And they are operated in the same way with the same controls.
Differences:
The PS-4300 has feathertouch sensor buttons for the start/stop and repeat functions, the PS-X5 has mechanical buttons for those.
The PS-X5 has crystal lock (quartz lock) feature, the PS-4300 has the traditional servo control with pitch knobs. The crystal lock feature is really convenient since you never feel the need to stare at the "moving dots" of the stroboscope and correct them with pitch buttons, like you would with the servo speed control of the PS-4300: it will always be on the exact speed.
It's a close call, but for me it would be the PS-X5 since it has the crystal lock feature, even though I like the weird styling of the PS-4300 more with the typical vintage Sony color, the electronic buttons with the dim red lights, the chrome buttons, the strobo dot style and the platter mat with the gel filled circles on it.