New vs. old DACs - opinions?

Some new DACs like Benchmark DAC1 do asynchronous upsampling with very strong jitter rejection. They sound great with any transport and any digital cable. It is very flexible (I use DVD player), allows long runs of digital cable or connection to less than ideal jitter-wise sources (computer card, ipod etc).

Since your intention is to buy DAC I would advise to get factory new one. Older versions of Benchmark, for instance, had some problems (they are at rev. G or higher now). I know of two. One was usage of Signetics NE5532 thin sounding OP-Amps until factory burned down (around 2001/2002)and Texas bought license for NE5532. They designed larger die and sound became fuller. Second problem was way to high output impedance on unbalanced (RCA) outputs. USB version has also better (stronger)output driver (LM4562) for XLR outputs allowing lower output impedance (important).
Additional factor is warranty - 5 years but only for original owner.

My own DACs are the Audio Synthesis DAX and Musical Fidelity TriVista 21, which sounds better at 96 than 192. This is also true of my friends MF 324. I have heard new DACs on other systems but not been motivated to purchase any. My own experience was reinforced for me by tests conducted by HIFICRITIC, which, like the early Stereophile, takes no ads. They found that the Zanden three box system was far and away the best with a rating of 105 on their scale. My 1992 DAX score is 45, the MF hasn't been tested. In a recent test of players the Moon Equinox RS scored 20, the Naim CD5i 11, the Bel Canto CD-2 25 and the Rega Saturn 29. They also tested a Rotel CD855 from 1990 and it scored 25. They also tested the MSB Platinum DAC 111 which is a very expensive DAC (10,000 pounds over there) and it scored 47. The reviewers conclusion was that "The current generation of DACs might have a great measured specifications, but they don't necessarily reproduce music as well as earlier technologies with less impressive measures performance. '24' bit DACs generally have excellent linearity, a low noise floor and the ability to draw power off low voltage supplies that make them useful in some applications, but musically I feel that they all gravitate toward blandness." He adds "the really good audio DACs in my opinion are all multi-bit types. Alas, few are now in production, and those few are expensive which means that you only find them in high priced players." This scenario should be familiar to you tube users [ I am not one] where a developed technology is discarded in favor of a new one that measures better and is cheaper and more convenient to build. The Zanden, Lab 42 and Audio Note UK are all multi bit chip users and sound very good despite inferior measured performance.

Your question is too general.

You need to compare specific DACs, old or new.

You also need to make sure the DAC, OLD or NEW, fits into you system well, for example, ratio of pre-amp input impedance to DAC output impedance should not be too low.

Another factor to consider based on you rcurrent system and listening tastes is whether you are going for "detail" or "smoothness" or some combo of both.

You also need to consider whether jitter rejection will be an important consideration for the DAC or no depending on your source(s). If you are not sure, then safer to go with a DAC that is more resistant to jitter from the source, like most upsampling DACS that must re-clock the bits.

How does the point system work? What are the factors and weights?

See the HIFICRITIC web site for info. Some of the ratings are there. They don't publish the articles as that is how the Mag is supported. As to Mapmans point, specific DACs will vary but whether there is a general trend upward or downward is a legitimate question.