Dear Andrew: You already stated that you can't go wrong with either tonearm and you are right.
+++++ " Will a Schroeder deliver dynamics, punch, bass suited to Rock music? Will a Triplanar deliver natural, timbral accuracy? Are both these arms suited to the same music? " +++++ You already receive the YES on these questions.
So what is all about: in my opinion almost only the tonearm designers could think that their design is the best one, unfortunatelly we can't take a tonearm choice only for its design there are several factors around that choice that we have to take in account: guarantee, quality control, price, which one likes you, with which one you will feel happy, wich one mates better to your TT, manufacturer support, inside wires quality, tonearm facilities and the most important of all with wich cartridges do you want to match.
This one factor is really critical to obtain what you are looking for: you can take, for example, a Shelther 90x cartridge in both tonearms and maybe you like more on the Triplanar ( example ) but this fact does not means that the Triplanar is better than the Schroeder it tell me that the 90X works better with the TP, that's all. Btw, there are some other tonearms alternatives out there like: Ikeda, Moerch, Brinkman, Phantom, Vector, SME, etc, etc.
Tom mentioned another top crucial link to obtain the best on the quality sound reproduction: the Phonopreamp.
+++++ " I'm attempting to achieve this same combo in an analog system but to an overall higher degree. " +++++
If this is what you really want then along with the tonearm/cartridges/TT you have to choose the right/best Phonopreamp for the task you are looking for: you can't go here with a lesser than the best device.
Regards and enjoy the music.
Raul.