As SSD will LOAD the game faster, not make the game RUN faster. But mapping should be faster, and FPS as well.
Once you go SSD, you'll never go back! I have 2 x AData SF1222 G2 Series SSD ($99.00 each) in RAID 0, and get reads over 540Mbps, and writes over 500Mbps. HDD may get 200Mbps reads, but more like 150Mbps.
If the game stutters it could be a HD issue, but the "popping of distance objects" is due to the game's LOD (level of detail) settings. The game will not render an object until it is a certain distance away from you. It has nothing to do with the HD.