RCA vs XLR which would say is the BEST?????


Here is the system:
1. Merlin TSM-M (right/center/left)
2. Axiom QS 8 rear channels (right/left)
3. (2) Earthquake Supernovas MKIV
4. Satori Shotgun Bi-Wire Speaker Cable (right/center/left)
5. Arcam DV 27 (no xlr connection only coax/optical/analog)
6. Bryston SP-1 Pre/Pro (coming with XLR connections)
7. Bryston 9BST amp (coming with XLR connections)

Now I need to connect the SP-1 to the 9BST so do I use RCAs or XLRs? I can do the in either .5 or 1 meter. I have enough RCAs to do the job now and I would have to buy the XLRs. I only want to do this once (right how many times have I said that in this hobby) so your advice will be welcomed. Which should it be?????
hammerfilms
How does one know if a component has truly balanced outputs (do you refer to the output impedence?). I have an MBL CDP2 which has physically both XLR and RCA outputs.
http://www.mbl-hifi.com/products/mblcdp2_en.htm
Dtanclim, short of opening up the unit and looking at the circuit (not something that will suffice in all cases or for all people), I would simply call up your dealer or the distributor and ask them - that is, if the info isn't already on the maker's website.
Dtanclim has asked a question that I should of asked. How does one tell? To all that have replied and read thank you for your time and trouble in this matter.