I may be able to give you some insight now that I've played with the SXI-Q software a bit on the ML. Whether or not this crosses over to the Sx450 only time will tell.
To start the SXI-Q is not necessary at all on the ML unless you want to do a firmware update or create custom output curves where you'd use S1-S5 rather than the Preset modes of Powerful, Powerful+, Eco, Standard or Soft. Everything else can be configured directly on the device. In regard to the power output the approach of SXI-Q is not the same as Escribe where in Escribe you can set a static Preheat for a static period of time when in Temp limiting mode. SXI-Q you set variable output levels with the use of 21 data points over a 10 sec period for either Power or Temp Limiting mode up to 100W in the first second on the ML. Another point worth noting is while it's necessary to use Escribe to set a custom TCR for different wire types it's not necessary to use SXI-Q for the ML as it can be done on the device directly but optionally can be done through the software. Also while Escribe attempts to provide approximations of real time data, SXI-Q does not and is mainly a configuration tool for the settings for the vaping experience. There's no Battery analyzer, Watt Hour calculator, Mod Analyzer, Atty Analyzer, Device Monitor etc.. that one would use within SXI-Q to get the device up and vaping.
The interface itself could use some work. It could use some mouse over help tags, more copy and save fields, direct input fields rather than drag and drop, disabling selections like Ni200, TI when Power mode is selected and probably more I haven't come across with my limited use, but overall it's not terrible. Being it's mainly a tool for configuring output settings it's much less complex than Escribe so easier to get setup and vaping for the average consumer. It took me all of 10 min to figure out how to create a custom curve, put it on the scope and vape it, all without reading the docs. But being less complex it will not provide any real time approximations either. For me, my device is configured and .sxc file saved, so most my config changes will be made directly on the device when needed and I won't be utilizing the SXI-Q software very often. It's a nice feature to play with if the Preset modes don't meet the needs of the builds, I've created 3 additional S1-S3 that I can select 2 are slightly more powerful than Powerful+ and the other is similar to Soft.
Personally I don't see the two apps being very similar. They have different purpose and features, one's required and the other is optional and each will appeal to different consumers.