Downside to R2R Ladder DACs?

Not true at. All , a quality resistor such as what you see in amplifiers, preamps last for decades, capacitors wear out before resistors , resistors control resistive values and dissipate very little 
heat especially in digital where it is low voltage .i have modded for over 20 years ,just think. How many years you may have Held
onto a a piece of electronics And it still works I have tunes 30 years old still working and quality resistors just  keep doing their job ,look at Vishsy naked resistors for example less then .5 watt
and rock solid used for years and tolerances on average well under 1%, if matched by the hundreds better still and won’t drift for many years wear a capacitor is constantly changing a resistor 
is a constant. I had a AbN 1704 R2R  dac for over 15 years sold it and still working .

cheeg your dealer doesnot sell any high quality R2R dacs 
that’s why all the misinformation a Lampizator, msg, Aqua ,
Denafrips .and and a bunch of otherbrand name  dacs made Today Are excellent . Waay too much misinformation .
it all comes down to the engineering and implementation 
of the design,your dealer is Totally bias ,I learned 40 years ago 
never put all your eggs in one basket ,there are a Many dealers online !!