Great question!
I have used both the PVC pipe, lacrosse ball and the Black 30" Extra Firm Rumble Roller.
IMHO, the RR is superior.
It seems to "knead" the tissue better through compression. The PVC pipe just "compresses" the tissue.
I use it daily as part of my warm up, especially on Quads, Hams, IT Bands, and Lower-Middle-Upper Back.
On Back and Leg days, I also find it beneficial to use it intra workout, especially when those areas are pumped with blood.
By doing this I can demolish those body parts and as long as I RR, I have almost zero soreness the next day. It's a marvelous recovery tool.
The lacrosse ball works better on calves and delts. It's a little more tricky to get enough bodyweight pressure on those areas with the RR.
The 30" RR is better than the shorter model because as folks have mentioned,
your body does move as you roll. Plus it covers more surface area.
True, it's a bit more expensive, but well worth the investment.
Good luck,
-MT