Is it not basically the same thing?The other form is just the bijuu giving more support/power,the rasengan probably just goes bigger.
I would prefer him doing frog related jutsus some of stuff Jyraya("nice" training he gave him) did but in lesser extent but meh the time for stuff like this already pass.
He can still advance his sage mode. Since both him and Kyuubi are friends now he can fuse with the toads so that he can have infinte sage mode.
Aside from Kishi actually making us give a damn about Naruto before we can give a damn about his power-ups, I think another problem is that Kishi powers him (and Sasuke, for that matter) up too often.
First he gets the sage, then he gets Kyuubi mode, then he gets Bijuu mode. All in the span of about 150 chapters, a good portion of which doesn't even focus on Naruto. As soon as he gets one power-up, he has to get another one as soon as the story focuses on him again. They lose all significance and meaning. Compare to Dragonball in which Toriyama spent entire story arcs building up and foreshadowing the next transformation.
Oh yeah, and I really don't see why Bijuu is such a big deal over Kyuubi mode. It's the same thing, just with a cloak (why he has a cloak, I have no idea) and bigger whiskers.
Bijuu Mode was foreshadowed. The chapter where Naruto and Bee were training for the Bijuu Dama jutsu, Bee told him won't be able to use the Kyuubi's full power if they can't get along. Naruto needed to be friends with Kurama to achieve that mode.
In Bijuu Mode he can use Bijuu Dama and his regular techinques are stronger.