That's a very fair opinion, but on the other hand, saying the amplification section of N7 is not as good as the amplification section of N8ii is, kind of endorsing Cayin for doing the right job in developing and pricing our products. .
For portability, I find the N7 amp section more than adequate with IEMs and low impedance headphones while on the go. Stacking with C9 at home, takes N7 listening experience further and bringing out the best of your gear.
In our past experience with C9, if you connect N7 to C9 in preamp mode, the overall sound signature will lean towards N7. If you connect them in line-out mode, the overall sound signature will lean towards C9.
In addition, the Line out mode also offers blacker background but the preamp mode can control the IEM/headphone better, especially with hard to driven items. This is because the C9 amplifier is operated at full power when connected with preamp input.
So there are proc and cons, there is no clear winner between the two.
I'm 50 / 50 on preamp vs LO but lean preamp due to N7's signature. As you stated, there's no clear winner but more flexibility to switch things up.