How easily can you distinguish between different DACs?

Sorry Jason, but all DACs do not sound alike any more than all turntable cartridges sound alike. Listen closely, pay attention to the sound and what you are hearing. Some DACs have better attack, decay, dynamic range, more musically accurate sounding timbres, with a darker background, and some people say, just as important as the sound, is the presentation in a soundstage (width and depth) and imaging. Many convincingly say that in the mid-price tiers, that an R2R DAC will offer better soundstage and imaging. YMMV because of your hearing, your training in listening, and such. To hear these differences, you do need to know what you are after - and what is important to you. After all two-channel audio is more than about "full range sound, for some people is about creating the illusion of a concert happening in front of you.

As John Darko says of the few standalone DACs he’s tested (none have been R2R AFAIK so far) that he loves the little Chord Qutest the most because it is the most musical to his ears. But he even says when doing comparisons that he can’t tell a huge difference, he calls it "splitting hairs". But to be fair, most of the DACs he has tested are in roughly the same price range. I’d like to see him get in some $4000 DACs and see what he says then in his nice acoustically treated listening rooms.

The thing is all DACs will make "sound". from a sub-$100 SMSL SU-1 to a $4000 Holo May. Whether or not you perceive a difference or a major one will depend on many factors. Most people CAN hear a marked difference between something as inferior as the onboard DAC in a WiiM Mini and pretty much anything else calling itself a DAC.  I own a Mini and use it with a Schiit Modi 3+ in my garage, and even the Modi is a noticeable step up. 

If you spend $1100 on a DAC then listen to a $2500 one and can’t hear anything much different, then simply save your money and call it a day. But know that there are people with ears and systems that can hear an improvement on up the food chain. I’d love to hear a $9000 Tambaqui DAC but doubt I’ll ever get that chance.

Right now I’m saving my pennies to get an R2R DAC, just not sure which one while I worry about longevity and serviceability after the warranty period is over.

On some DAC’s it’s night and day and some it’s very subtle.  For example, I have a Schiit Bifrost and a Denafrips Pontus ll and they are night and day different! 

They don't sound the same to me at all even at approximately the same price range. Right now I'm comparing a Denafrips Pontus ll against a Tubadour lll which are both R2R.Initial impression is the Tubadour is clearer with a cleaner attack. The Denafrips rounds the edges off.It reminds me so much of a CJ (tubed) preamp I owned years ago.Quite a surprise.One is not better than the other,just different. It's easy to tell the difference even with my old ears.No way I could afford a 12k dac,even though I'm curious,but not enough to search one out.

No two most anything ever sound exactly the same but the good news is that it’s getting harder to find a bad sounding DAC these days. It’s more of a personal preference thing. Digital streaming technology overall is very mature these days and the wide range of quality products at all price points reflects that.

On a scale of 1 to 10 speakers are a ten in terms of being able to discern differences. Amplifiers are an 8. DACs are more like a 4-5.  

You have received some insightful comments to your question.

My experiences mirror @mikelavigne (i.e., "most dacs are decent"), @czarivey's comments on "voltage output", and @ghdprentice regarding the presence of "distortion and high frequency trash".

Of the better DACs I have owned and/or auditioned for a time in my own system, they all sounded mostly "acceptable" yet there were indeed differences that in my world typically lean toward the perception of either greater resolution or tonal density.  I don't care for what some may characterize as "warmth," as I believe that indicates clouded clarity, probably resulting from distortion.  I want clarity that a high S/N provides, but the absence of tonal density and dynamics/impact are deal-breakers for me.  I do believe you can mostly have both but you may need to settle just a little on one side or the other and, if the DAC sounds good, you will likely forget about those nuances after owning it for a while.  The DACs I like seem to display a rich tonal density and dynamics/power fully across the volume range, i.e., you don't have to chase the volume control to achieve impact and tonal color.  My goals are more about getting the midrange and bass right, but the high frequencies need to sound natural without roughness caused by "distortion and high frequency trash" .  Clearly, the rest of the system needs to be able to keep up.

IME, there are certainly audible differences that you can notice upon first listening to different DACs.  However, in many cases with better DACs, the differences may be subtle so you may need to listen for a while and do some A/B comparisons to pinpoint exactly what the differences are and how they affect your listening enjoyment.