Yes, by and large they do. I'm very conservative with my string choices; when I started out I said that if I found strings that I was comfortable with I'd stay with it rather than continually swapping about as some do here - no names of course! That oversimplification has its advantages but who knows, there could be some very nice choices out there that could transform my playing/ sound.
Anyway, back to the subject. I've been very happy with Mitts. They seem to suit the jazz work I do and the tension has never been a problem. They need a bit of playing in after initially making the bass sound like a banjo. To date, all the basses I've owned have had the Spiro sound except possibly the Martin Concert that Ive just traded in. Acoustically it was quite dead and initially disappointing but once amped with an Underwood it produced a nice mellow, almost old school sound, that brought me many compliments.
Just as an aside, when I first visited Martins they were very orchestral and had very few jazz customers, even none at all perhaps. They had a nice bass that I felt could benefit from some Spiros. This seemed new to them so they put some on, took the bass to the ISB convention and got a commendation for tone. They credited me with that!