Firstly - my review is for the PC version which means I have all the graphical bells and whistles at my disposal plus PhysX as I use an Nvidia GPU. If you are looking for a similar experience to that found on the consoles, I'd suggest having a high 5xx (560Ti upwards) series Nvidia GPU or it's equivalent ATI GPU as you'll need to run the game on the high preset; explanation is below.
The console versions, expecially the PS4 version, both look fantastic so if your PC is running older hardware, I'd seriously think about the console version as they have a mixture of the PC's 'high' setting (this combines some of the very high settings with some lowered settings) but lack tesselation, volumetric lighting, motion blur and PhysX which does make a significant difference.
Metro 2033 has the biggest overhaul; most are positive and the tweaks to the game play are welcome. Last Light has a few visual tweaks but little else. The graphics have a slight downgrade to them; don't know why 4A did this but it's apparent when you compare Metro 2033 to the Redux version (Guru3D has screens for the curious).
I'd recommend the Redux package if you are looking for a different FPS experience; Metro is a story driven FPS about survival (LL is a little more run and gun) and features ghosts, anomalies, mutants and human enemies. The game play doesn't hold your hand and can be played in a stealth or shooter styles.