Title 50lb bag or 70lb bag?

Does anyone have either or the 50lb or 70lb heavy bag? I guess they're the same width and height 14"x42", but the 70lb bag is harder, but how much harder and how much softer is the 50lb bag? I have a 40lb MMA double end everlast bag that is 12"x30. Is real small and it's pretty soft. Mainly used for footwork and slipping as it's hung high. Then I have a 100lb Nevatear Everlast Worldwide bag that won't budge.

I guess my question is how much difference is between the 50lb bag and 70lb bag and should I just get the unfilled bag and stuff it myself? I don't want the bag to have too much swing, but I also want it to feel somewhat soft on my hands. I'm looking at the synthetic leather bags.

I like the resistance in this Title bag that pacquiao's hitting. But then again, it might have been stuffed by his gym and not Title. Does the 50lb Title bag have this much resistance or similar?
http://www.youtube.com/watch?v=i7dB_4yXPv4