Straight XLR vs XLR to RCA adapter

Defeat the purpose of what ?? If you are talking about preamp gain, no it does not.

This will depend on the equipment. If the electronics are fully balanced throughout then your best cables will be XLR to XLR but if the equipment is not a true balanced design than it is not a big deal.
Contact the company and find out if your equipment is 100% balanced.

Thanks for everyone's responses.  I don't know if theses facts make any difference but let me put them out there.  My preamp is the Jaton  RC 2000P   Operetta . Amp is   Audio-GD SA-300 SE.    Speakers are Monitor  audio silver RS 6  

I was able to speak to  both King Wa of Audio GD and  George of Jaton.
George says of the RC 2000P that from their test the XLR measures a 6db lower noise floor.  When I asked  King Wa he just said I could expect a 15%  improvement in sound.  Lower noise floor here as well?   He did not elaborate. It is with  these things in mind that Make me want to try the XLR connection. Having said that it would seem that the only way to see any Apple to apple comparison is to get a the GA-0 in XLR As currently I halve the RCA version.

Using RCA/XLR adapters on regular RCA cables makes no sense whatsoever.

Agreed. Did not work at all for me.