Yes the 150 is harder. I know that the 140-150 contain spool pins, but because they are made better then the junk masters (#1, #3, #5, etc), they are better locks to practice on because they actually feel like real locks
But really when you think about it, you might be tempted to say,
"but wait a minute, if the #3 is so crappy and gives so many people problems it must be harder!"
Not true. It's crap yes, but most can pick it pretty easy, and if you can't you can always rake very easily. The 140-150 have spool pins, not as easy to rake, and will throw most noobs not use to spools.
That said, you should know that the master 140-150 are the easiest locks with spool pins, and great to practice on! Better quality, better feel make them a great way to learn how to pick spools. But they are masters! And if you can find that sweet spot after the plug locks up, all it takes is to ease off the tension a little and push that pin up more and it will open. In other words, after you picked it once, you will be able to pick in a minute after that
