Yes, you'll have to tell us what you want to use the keyboard for. The touch of the DGX and the P series are VERY different. Even though they advertise DGX620 has graded hammer action, it will feel very much lighter than P140 - more like a heavier synth action to me. DGX620 belongs to the portasound catogory (ie it has rhythms and arragements etc), P140 is a digital piano and does not have those. I believe the sound will be different too - I haven't tried the DGX620, but if it uses the standard DGX sounds, then the piano is nowhere close to P140. Don't get trick by the specs saying they are AWM - ALL sounds from Yamaha are AWM. You have to listen.
So, they are really 2 different animals.