I tested the new snapshot today and I have strong differences between the Snapshot Version and the 1.7.5/1.79 with the Frames per Seconds and Chunk Loading.
Minecraft 1.7.5 - Up to 30/200 FPS
Minecraft 1.7.9 Up to 30/200 FPS (both without mods)
With the Optifine Mod I'm gaining even more FPS (lowest: 25, max: 250)
Snapshot Version: Between 1 and 8 FPS.(I already tested the 14W27a and the 14w29b and it's decreased highly from my normal standard.
I hope you handle the resources as well for all Clients without a high qualified Gaming PC or something like this.
Please do not select Future Version 1.8 as affected version as it is only for the developers to say when a bug will be fixed 😉 just use like you did the latest snapshot version / the version you are playing 🙂
Can you maybe add some information about your environment (graphic card, processor...)?