I use both Craigslist and Offerup to sell things and although I do sell quite a bit of things through Craigslist pretty fast I find I sell more stuff using Offerup than I do with Craigslist.
But it's great to use both websites to sell things because you tap into a much bigger pool of buyers for your stuff so I would recommend to use both Offerup and Craigslist to get the most sells.