PC Upgrade Help: Ultra-Widescreen + FreeSync vs. 144hz Monitor

So I've been wanting to upgrade my GPU and monitor for a while now and I think I'm finally ready. I've decided to try an AMD card after rocking a stock EVGA 660 Ti for almost 3 years now and I've decided on a R9 390 (The cooler/company will probably vary based on sales, but I'm not making the same mistake of buying a stock model). You can comment if you think that's a bad or I should get something else, though that wasn't my reason for posting...

I wanted to either get a high refresh rate monitor or an ultra widescreen for around $300 (US). I found the LG29UM67 link here which seems like a good choice in of itself, but it also has FreeSync which made it even more attractive. But would it be more better to get a nice 144hz Benq monitor for around the same price? How much would I benefit from FreeSync or a 144hz panel?