I don’t believe there is any difference between the two really. Your variables in a bag of meth are L-Methamphetamine, D-Methamphetamine, and cuts of various kinds some of which may be psychoactive but usually are not. Different proportions of the two isomer/types of methamphetamine can lead to different subjective experiences. D-meth works more on your central nervous system and L-Meth more on your peripheral in the sympathetic and parasympathetic nervous system. That’s why different batches feel different.
I would theorise that more L-meth in your mixture can give a higher rush when shot, because it activates the ‘flight-or-fight’ response in your body. So if you get a big ‘bang’ when you shoot it but not a lot of euphoria that might be one explanation.
If your high is very smooth and euphoric and your heart doesn’t go nuts and you don’t start sweating or breathing fast, then I’d theorise you’ve got mostly D-meth mixture. Although a big dose of pure d-meth will DEFINITELY make all those things happen too. I’m talking about relative effects for the same sensible sized dose.
The difference might also be just straight out purity. With a low proportion of meth to cut. The sensible thing to do if you will be shooting is to acetone wash the mix which will increase the % of meth overall in the mixture (for most cuts you can make an 80 % pure bag a 95 %+ bag with a single quick wash).
I did have a dealer once swap me a different product when I told him I was going to shoot it. He said, the original one he gave me was for smokers. I suspect that meant it was more cut. If you are shooter, you know how much MSM and some other cuts there is as soon as you put the water in your spoon. MSM crystals stand out like dogs balls and take forever to dissolve. Meth dissolves pretty much instantly at room temperature when crushed..