IMO, the Kweld is just a better welder. Firstly, it is able to measure
energy input per weld (rather than just pulse duration). In theory, this should produce more consistent welds, and allow you to set it up more consistently. Also, the development and usage has been well documented here (44 page thread), so you get good support and lots of examples. If I was going to buy a welder, this is what I would buy.
https://endless-sphere.com/forums/viewtopic.php?t=89039
The Malectric welder looks fine. It doesn't have the same large user base here on ES forums, so it is a lesser known quantity. In theory it can probably handle about ~75% of the current that the kWeld can handle, so it won't do quite as heavy strips. The website says it can do 0.25mm nickel strip with an 800CCA battery, which is probably as thick as you'll ever need anyway.
So that's the comparison:
kWeld: more expensive, easier/more consistent to get set up, slightly more powerful, better support.
Malectric: cheaper, probably does the job fine, better $/weld value.