No real pros and/or cons - it just depends on your system. On some systems, the jump from 120 to 50 et6c can produce stutters. On others, it's not noticeable. There are some who run limited around cities and unlimited in rural areas with good luck.
The frame NUMBER is not important - turn OFF the frame counter and change your settings until the system looks good to you. Which would you rather have - 120FPS with stutters and pauses or 15FPS smooth as silk?
I7 3770K @ 4.73ghz Asus Sabertooth Z77 16G G.Skill 1600 7-8-7-24 2T EVGAGTX680 Corsair 1000W PSU 2 - 2 - 256G OCZ Vector SSD - OS & P3D HAF 942 - Corsiar H100i Liquid Cooler W7 64 Home Premium.