-After reading this chapter and the following chapters it seems that Rikudou mode lacks in power and control. When Naruto first showed Rikudou mode and sucker punched Kisame he injured his leg from slamming on the wall so hard.
Sage mode also makes his body impervious to physical damage.
-We see next that while entering Rikudou mode the Kyuubi steal Naruto's base chakra so he can't stay in the form for long, we don't know how long but that's still a factor.
Sage mode increases Naruto's chakra to at least 2 or 3 times its normal state so the kyuubi absorbing Naruto's chakra wouldn't be so bad.
Now we see that the biju rasengan requires a great amount of chakra control and the sphere is great in density so great that the ground around Naruto's feet, the floor was broken.
Sage mode grants Naruto unimaginable strength to the point he could stop a raging rhino easily and then toss it in the air. In sage mode Naruto could create a rasengan with one hand also his fight with the kyuubi showed he could actually use only one clone for the FRS, Naruto's chakra control is greater
Naruto always can't complete something without anther thing. Example For Naruto to use a rasengan without clones he has to be in sage mode, another would be in order to use sage mode Naruto has to use clones, He uses clones for his rasengans.
Rikudou mode seems to have a special power over nature that might even play a special role.