The thing about BPB #15 is that green is so sloped. Sure, if you are below the hole and not too far off line, it's not a hard putt. But if you are to the side, you have a wicked, wicked downhill break, and if you are above the cup, your putt is going to travel at light speed.
I might say that BPB is easier than Oakmont #9 to get on the green. It is possible to get quite close on BPB #15, even to eagle. Oakmont #9, I think I have hit GiR once. Though I think that hole is so hard in part because I am not long enough off the tees. I'm usually hitting long iron or wood to that pin and with the raised burm at the greenside edge of that trap, the only way to clear that is to hit off the back of the green. However, I'd rather be hitting out of that trap in front of Oakmont #9 than looking at a 15' side putt on #15 at Bethpage. I think that hole can turn a three putt faster than any other hole I have seen, no matter where you are save directly below the hole.
#17 SA is the same, frankly, as #9 Oak to me. I have to hit too long a club into the pin that the raised trap in front is a ballcatcher, or I'm off the back of the green. The alternative is to shoot for the fat part of the green, but if you have to be careful on that hole because you can end up with fringe, rough, or even trap between you and the cup while on the green. Both Oak #9 and SA #17, once I am safely on the green, I heave a sigh of relief. At BPB #15, that's when the fun really begins.