Does EPPM cover everything PPM has?

I am considering to buy Primavera P6 PPM or EPPM

1- Is PPM a subset of EPPM? In other words, if I buy EPPM I can do EVERYTHING that PPM does, and more? If I have EPPM, can I still do the good old windows, desktop based schedule making like in PPM? Or because it is EPPM, everything, inlcuding making the schedule itself is web based?

2-Is EPPM looking and functioning exactly the same as PPM and more? I mean if desktop operation is possible for EPPM, does it look the same as PPM and only when I go to web it has mote things? in other words, can EPPM be operated offline on desktop and in excatly the same way as PPM?

3-i read somewhere that EPPM doesnt have network diagrams, is it true? what else it doesnt have?

I am just one man show scheduling operation right now. So I know you will say buy PPM but for just $ 250 difference, if EPPM has the good old PPM and more then I will buy EPPM. But if EPPM doesnt have many things that PPM do then I will think about it