Having years of experience using a sawzall for demo and finish work I noticed that there is a difference in the angle of the blade .
I prefer a straight bled for having control of the saw. The angled blade s are great for ripping thru stuff quick.
I also prefer to cut free hand rather then use the guide. When cutting the frame for a nice straight cut angle the saw back so it is more parellel to the work. This helps keep you cutting straight.. And go slow but be sure it cuts and don't sit. That will dull the blade. On finish work it sometimes is better to use a slightly used blade rather then a nice new sharp one fror more accuracy. Chose a medium # of teeth per inch like 18.