Assuming that there aren't any major gotchas, I think that the alleged improvements over the Rigol would be worth the money, even at 100MHz vs a hacked DS1054Z.
The DS1000Z series is really not satisfactory at 100MHz with more than 2 channels enabled, or at low signal levels, or when using the FFT - I especially had issues with the first 2, and they were factors in my decision to upgrade to a (launch-promo) RTB2004. That said, the DS1054Z is still at an amazing price for those with very tight budgets, and will do the job for many - I was never unhappy about buying mine!.
Given the free serial decodes (particularly important for us), I'll be suggesting at work that we grab one of the Siglents (hopefully I can nudge them towards the 200MHz option). As we can't really hack Rigol options when using them commercially, once you add the serial decoding option the price difference basically disappears even if you don't want the 100MHz bandwidth.