I've also used synthetic bags, especially when cost was more of an issue than it is now (empty nesting is VASTLY underrated!) They always performed well, and there's nothing wrong with using them. However, there was no going back once I got my first down bag (a TNF Blue Kazoo, back when North Face bags were held in somewhat the same awe as Western Mountaineering bags are now.)

Price does matter, a lot; quality matters even more. Given the choice between spending the same amount of money on a lower-tier down bag versus a top-notch synthetic bag, I'd probably choose the synthetic.

By the way, I've also used the Marmot Hydrogen and Helium, and they're quite good, too. The ratings are pretty much dead on, not conservative like the WM appear to be. (For the same temperature rating, I found the WM bag to be warmer.)