Is a captured good tonearm cable better than a high quality one DIN connection?

What exactly have you purchased, and what exactly do you propose to do? it sounds like you have purchased a triplanar with a continuous cable from the cartridge pins all the way to the inputs of a phono stage. If that is the case, then no it would not make any sense to attach that cable to a box so you could then use your expensive interconnects into the phono stage. Anyway, so far as I know, the tri-planer is offered either with a continuous single cable such as I just described or a short external cable that terminates in a box with female RCA connectors on the other side. It is not conventionally offered with a DIN interface. But I suppose you can get it any way you want it.

Use the continuous.  Sell the $4k cable or use it for your second arm. You do have a second arm..?

A $4,000 tonearm cable? Damn, how much was the arm it was used with?!

I am certainly with lewm on this. On an arm like the Triplanar you do not mess with the cable. Direct is always the best and the only way I would ever order an arm. Some makers like Schroder will give you a choice of cables usually offering different metals, copper vs silver. They will usually now give you a choice of terminations as many of the best phono amps now use balanced connections. But, the cable is always a direct run to the cartridge clips. 

If all things were or are equal, which they rarely are, a single run of cable from the cartridge body to the RCA jacks on the phono preamp --- is best.

the hardcore used to run van den hul mono-crystal wire from the cartridge clips back to the RCA’s on the phono input.

the most far gone among us (I’ve done this myself) would hardwire the mono crystal wire to the board of the phono preamp, via removing and eliminating the phono preamp chassis mounted input RCA’s. Where one has to take the phono preamp apart and de solder from the board, in order to decouple the tonearm from the system.

"Worth it", as Deadpool would say.... 

Thus, only two solder joins in total, one single wire. Cartridge clips and board soldering and the set of clops and their friction fit on the pins.

Some go one step further and solder the wire right to the cartridge pins... 33% mo-better (from three to two points)...

It is exceedingly doubtful that any captured phono cable is actually the same wire from the cartridge pins to the outer male RCA jacks, on the output end of the cable. There will invariably be two types of wire involved, with a set of solder joins in the middle, right where they join..