In my upright bass playing history (about 25 years now) I've had 3 Kays, 2 Strunals, 1 King, 1 Shen and my current Jacobus Hornsteiner. Some of these basses sounded better with steel than with gut. A louder bass that has some boom seems to lend itself to gut, and my current bass is the loudest and boomiest I've owned. I love the full set of Gamuts on it, and I can even bow on them without wincing (Pistoys are an improvement IMO) Other basses, like the Shen, had a very nice sound, but not real loud, and Spiro Weichs were my favorite on that one. The King, believe it or not, did not project all that well with guts. Billy Linneman told me that the King was the more expensive of the H.N. White basses, with more bracing and detailing, but the American Standard with it's big body became more popular. The King sounded awesome with Corelli 370s, and they were good for the long string scale. Both Strunals were pretty good with guts, OK with Spiros, best with Velvets. The Kays were a mixed bag, they sounded equally crappy with Spiros or guts

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So I guess my main point is that I've found that it takes the right bass to make guts really shine.
These days I bow on the Gamuts mostly for intonation practice. I bought a cello some time back, and when I'm looking to make a real arco tone, I play on the cello. My goal is to be able to play well enough to do a little simple live and studio work on the cello. It has Evah Pirazzi strings and they are a total pleasure to bow. I have to agree that plain and roundwound guts are not the best choice for arco playing, although bassists made do with them very well for many years.
There were a few times that I had 2 basses, one would always be set up arco-friendly. But I came to realize that I was really trying to emulate cello most of the time, and I've been too lazy to develop much thumb-position facility. So for now it's all gut pizzicato, and arco cello, and I've been pretty happy
