So here is the issue: The standard Python SSD miner carries 198 tons of LTDs. I can fill it up in around 25 minutes. For the sake of the argument, let us consider the same build Krait (just removing a cargo rack). Such a build would be capable of carrying 134 tons of LTDs. With the same mining rate, the Krait would fill in 17 minutes, but let us be generous and say that you can shave 2 minutes off due to better visibility and speed (speed is only really useful in getting from rock to rock and the Krait only has about 10% extra speed so this is really giving the Krait more of a boost than what it likely will have). This would make the Krait take 15 minutes mining 134 tons.
Now, here is the issue, you will not just be mining, you also need to off-load your mined cargo. The ships will not differ much here so let us assume this takes x minutes. The total haulage rate of the Pythonis then 198/(25+x) and that of the Krait 134/(15+x). In order for the Krait haulage rate to beat the Python’s, we need (approximately) x < 6. Remember that this is allowing the Krait more of a mining boost than what I find reasonable.
Now, unless you are selling to carriers in system, your non-mining time will likely far exceed 6 minutes. In fact, 6 minutes is about the non-mining time I have when storing the LTDs in my carrier next to the arrival star one jump away.
NB; If you mine slower than I do, non-mining time will be proportionally less relevant, which a priori could benefit the Krait.
NB2; If you use the SLF bug (rumored confirmed as bug and due for fix) - you obviously cannot use a Python as it cannot carry a fighter.