Which USB implementation, Benchmark built-in or ?

How good is the implementation of USB in Benchmark DAC1 compared to the one in Audio USB Off-Ramp Turbo 2?
Essentially, what is a better way to go, use Benchmark DAC1 and its own USB interface connected to PC, or use Off-Ramp USB to S/PDIF converter, and go S/PDIF into Benchmark DAC1?
The Off-Ramp uses a low-jitter Superclock4. The Benchmark DAC-1 USB uses a simple inexpensive crystal. The Benchmark DAC-1 USB sounds very nice, and the reclocking that upsamples to 24/192 does help eliminate some of the jitter, but there are quite a few areas of improvement still possible. The stock unit is a great value though.
Considering the well-known deficiences of the S/PDIF interface, why bother with a USB to S/PDIF converter when you can get a cleaner solution with the Benchmark USB DAC1 that eliminates S/PDIF altogether?

Elias Gwinn, a Benchmark engineer, recently stated on an audio forum that "the USB signal is first converted to I2S, maintaining its original sample-rate. I2S is a fundamental form of digital audio. When an AES/EBU or S/PDIF signal is streamed to the DAC1 via XLR/coax/optical, it is also first converted to I2S at its original sample-rate. The front panel switch chooses which of these I2S signals are sent to the next stage: the sample-rate converter (SRC) chip. This converts the sample-rate of the I2S signal to 110 kHz, regardless of the original sample rate."

Search this and other audio forums and you'll find that S/PDIF has significant flaws, including poor error correction. High end audio has been saddled the S/PDIF interface, but now Benchmark and other manufacturers have developed USB DACs that eliminate S/PDIF from the signal path.

The bottom line is that if you are considering a Benchmark USB DAC1 or the non-USB DAC1 which requires a USB to S/PDIF interface, you will be better off with the former.

I understand what you are saying, and I tend to agree.
However, an external USB to S/PDIF converter offers flexibility in choosing a DAC of your preference.
I have not heard Benchmark DAC-1, based on some reviews it sounds cold and analytical, for this reason I am reluctant to buy it.
So my dilemma is, will this additional and seemingly unnecessary conversion to S/PDIF in an external converter destroy all the benefits you may gain by selecting a DAC you prefer that does not have USB interface?
It would be an easy choice if I could hear and compare all the devices, but it is not possible.
For example, do I go with USB to S/PDIF converter driving my MF X-DAC, or LavryBlack DA-10 which I am considering as replacement for MF, or do I go Benchmark DAC-1 with no USB to S/PDIF converter in the chain, assuming Benchmark will outperform any other DAC fed from external USB to S/PDIF converter, simply because of this additional conversion step.
What a pain this hobby is.
Conversion of USB to SPDIF externally does not necessarily kill the sound. I believe some of these converters are better than others though, and like all gear, a bit system dependent. These do give you the most flexibility with choosing a DAC.

I believe any USB DAC that converts the USB to SPDIF instead of directly to I2S is probably not worth your time. To my knowledge this leaves the Wavelength Audio DAC's and the Benchmark (which I just learned from this thread that is converted to I2S -- I did not know that before) Any others?

Also, regarding the Benchmark. I believe the charge that it is too clinical/analytical sounding was levelled in its introduction (first year or so) and I believe in recent iterations they have corrected this (this is just from my reading, not my experience though). Either way though, there are legitimate WEB retailers (Audio Advisor, Audio Revelation, etc.) whom allow you a 30 day trial. So, there is really no excuse not to demo in your own system. You may even be able to find a dealer who will let you hear Wavelengths stuff on trial as well -- That is the ONLY way to know for sure.

I am still trying to sort all this out myself. I love my Attraction DAC and have yet to hear another DAC that I like better. So, for me, I am trying out USB to SPDIF converters until I can find the one that works best in my system.
Your follow-up indicates your situation is more complicated than a simple choice between a DAC1 with USB or standard DAC1 with S/PDIF or AES/EBU inputs. My experience is limited to the DAC1 connected via an M-Audio Transit and Slim Devices SB3. I've run both directly into a Bryston 14BSST (the SB3 via RCA unbalanced and DAC1 via balanced XLR).

From reading numerous reviews and owner comments, I suspect the difference between the DAC1, Lavry 10, and other top quality DACs is very subtle and influenced by the Placebo Effect. And frankly, I'd be surprised if there is any appreciable difference betweeen the standard DAC1 and DAC1 USB. Your choice of a power amplifier could have a much greater impact, for example, going from tubes to SS. I'd personally go with the USB version to avoid a USB to S/PDIF converter, while retaining the option to connect via S/PDIF to other sources.

I would note that the Benchmark DAC1 seems to be holding about 75% of its value for resale on Audiogon, so you can probably buy it without a large financial risk.