Which is better - Hi end CD transport or Music server into DAC?

Guys - I have the Music Vault diamond server which is great- My question in which is better a hi end Transport into my DAC or the Music vault sever?- strictly thinking sound quality- thks
If the DAC is well made it should sound equally good with either source provided the digital data is bit perfect.
+1 here. A high quality, multisource DAC is essential (Wyred 4 Sound DAC2SE for example), as is a CD transport (PS Audio PWT) and server (MacBook Pro is what I enjoy), and, especially, a multitude of good analog sources (I just had to get that in here :-).

If one currently owns no CD’s/SACD’s (a rather young person, presumably), and asks the question to help decide whether or not to start buying them, keep in mind the cost of building a disc library. At, say, ten bucks a disc, a modest collection of 1,000 titles will run $10,000. I have somewhere around 3500, so even if streamed-sources sound better, I need a transport. It’s kind of late to start buying CD’s now, though they are much cheaper than they us to be, and will in all likelihood be even cheaper in the not-so-distant future.

I would go with the music server or a dedicated music computer as I have , stick in some of Mark Porzilli's software which retails through Laufer Teknik and get a PS Audio Lan Rover and you will have a killer digital system.
Neither. The best setup is using a network card inside the dac, for example the Bridge II cars in the ps audio DS or the DCS network card. Sell all the so called ultimate usb cables, all you need is a good Ethernet cable (say cat7 or cat8 from audioquest for example), high speed internal network, and a good/fast internet, preferably using fibre because it’s quieter.
Since I build a "high end DAC" with a 35lbs power supply I have used both CD transport (too many to mention) and server into the DAC using HDMI cable as I felt with was the best sound.  IMO only, the two offered excellent sound but different.  The transport offered a more emotional sound in our direct comparison.  The server offered an excellent soundstage with really nice details.  It was very nice to listen to but certain instruments just did not sound as emotional as the transport in direct comparison.  I could live with either as long as I did not have to compare them side by side.  Hope this was helpful.  Happy Listening.
I have an older model Music Vault paired with a Luxman DA-06 DAC.   I tried feeding the same DAC with an older CEC transport and a PS Audio Perfectwave transport.  

The Music Vault beat out both transports.   The CEC was the better of the two transports, but it lacked detail and was flat sounding  compared to the Music Vault.   I expected to like the PS Audio Perfectwave transport based on all of the glowing reviews, but was unimpressed.
Arguements that a high end disk spinning transport will offer sonic improvements over a well implemented server based system are few and far between these days for good reason. 
As I learn more about digital audio, I'm appreciating that while "bits are bits", the timing of those bits when they arrive at the DAC are very important to the ultimate sound quality.  DACs do have clocks as part of their design, to "re-clock" those bits that arrive at their input stage, but "re-clocking" can only do so much to correct for timing errors.

I suspect, with your particular set of components the port on the Music Vault and your DAC just pair better together than the other options.  I'd recommend you look into a cable upgrade, as that will likely further improve the sound quality.
The best that can happen here is that each person can relate their own experience.  In my case ripped CDs on a HD sound better played through a simple ASUS laptop via USB than they did played directly through an Oppo 105 by spdif.

As @ejr implied, bits are not simply bits.  The timing and quality of the analog (yes, analog) stream of bits makes a great deal of difference in the ultimate SQ.
Transports are. It created Raquel, each unit should be treated as an individual. IOWs, can’t answer the OPs question favoring one device over a different one in these 2 categories. 

E.g. in a/b tryouts,my SimAudio CDP (Equinox, $3000) from 2007 absolutely killed the transport on the OPPO 95. While the Bel Canto dedicated cd transport($1500)  was also better than the OPPO, and right on par with the Sim in terms of SQ, tho slightly different sound. 

Why? I think bc the Sim has 2 dedicated power supplies for analog and digital. But the OPPO has 1 power supply for the 100 different functions it has, so the transport quality suffers.
I prefer my networked music system with SPDIF at the endpoint feeding a Multibit DAC. Most of my CDs were ripped with the transport of a common PC computer.
A high end music Server, truly optimized for music playback, will top any general use computer that is being used for music playback