Both welds are MIG. The second photo's welds aren't penetrating as deeply, I'd turn the amps up just a little more.
The weird thing with welding is that you can have the welder, feed, gas and metal all perfectly prepared and tuned in and getting awesome welds; repeat every setting the next day and you get crap welds.
So long as you're getting appropriate penetration, the difference between a good weld and a bad one is the time it takes to get a grinder to it
