Aoliviero,
Cello, Teres, Thom Mackris and I have offered detailed sonic comparisons of these arms several times. A search should turn up those posts.
You asked some shrewd questions, which indicate you've already got a handle on the key differences.
Will a Schroeder deliver dynamics, punch, bass suited to Rock music?
Yes, absolutely. Frank Schroeder enjoys leading edge electronica. If his arm didn't rock he'd fix it.
But a TriPlanar VII will do it slightly better.
Will a Triplanar deliver natural, timbral accuracy?
You'd better believe it, at least with a top level ZYX. I'm spinning Solti's 'Siegfried' as I type, and Fafnir sounds as real as any dragon I've ever spoken with!
But a Schroeder Ref will do it slightly better.
Are both these arms suited to the same music?
Yes, depending on the cartridge.
IMO neither arm is "better" than the other. They are more alike than different, and either one's small differences could be preferred by certain listeners or in certain systems. Do you prefer Art or Science?
***
Like Diamond007, I'm distressed by the poor support from the current owner/builder of Herb Papier's wonderful arm. Improvements suggested by multiple owners are ignored. QC and consistency often fall well below standard for a product at this price point. Ship dates are missed. Communications from both dealers and owners go unanswered.
Two years ago I encouraged Mehran to carry the TriPlanar, thanks to its wonderful synergy with all the top ZYX cartridges. But if Tri-Mai doesn't get his act together he could destroy one of the finest products in the history of audio. Anyone interested should buy one before that happens. Assuming you get a fully working copy it could be the last arm you'll ever want or need.
Cello once asked Paul and me if we'd take a Schroeder Reference for our TriPlanar VII in a straight trade. We both agreed that we wouldn't. It's truly that good.
Doug