Hi.  my idea is to leave the fsx where I fly PMDG 737 and 747 V2, and go to P3D that also has those planes, but improved.
 Besides, basic scenarios, to make it look pretty, which I need, or rather, textures, I don't know what to call it.
 I would also like to ask, to the same Pc , is the best performance of P3D compared to Fsx noticeable?
 My current pc (proccesor 4790k oc 4.7 gz, 970 gtx 4gb oc, 16 g Ram ... would move the P3D better?  With so many screens? I have 3 outputs for 3 tv main view, and forth one matrox (3 screens for instruments). I have a fith one usb graphic card for 27 inches touch monitor) with fsx in fligh I have 20 frames. In Barajas Madrid,  with all parameters full, 10 frames) 

Do you think with this pc it works better with p3d v4.5? 
 Greetings.

Complex planes and 3D objects tend to kill the fps in P3D (just as they do in FSX).

However on a whole and with the same hardware P3D runs much better than FSX.

e.g. no Out Of Memory crashes, DX11, Dynamic lighting, no 6% scenery loading hanging and a whole bunch more.

That said many GFX operations have been pushed over to the GFX card meaning you would need a powerful GFX card, I run a 1070Ti overclocked to 2 Ghx and it is not enough to go beyound 4 SSAA, plus I reguarly top the card out at 100% and about 75% of its 8GB of ram meaning careful tuning is required, as once a GFX card maxs out frame rates drop like a brick.

You could just buy P3D anyway, it's probably way cheaper than those planes you're going to have to re-purchase.

That way you could try it out and decide to continue or not.

Here are a couple of links to help you make up your own mind.

This one is P3D and FSX-SE, with majority the same addins flying the same airport in the same plane on the same hardware.

And here is a link to a tuned P3D describing what made it so.

https://orbxsystems.com/forum/topic/188575-p3d-v45-maximum-detail-and-performance-tuning-test/

Hope it all helps...

Cheers