I've used both, and they both generally work the same (and @cryotosensei has already summed up a lot). Only things I can add are that A) Bitcoin Co is BTC-only (so if you don't want to support a company that also deals in eth, etc, that's a difference maker), and B) BitRefill tends to have a wider selection of vendors available (though I haven't checked on books specifically).

• Bought food takeout vouchers with the Bitcoin Company
• Go download the Bitcoin Company app. It gifts you 1000 sats for bookmarking your favourite brands
• I like the Bitcoin Company more than Bitrefill because the former gives me more cashback rewards. Also, I can use the rewards to offset my next purchase. This is unlike Bitrefill, in which I must accumulate the cashback up to a certain amount before I can use it to buy a gift card.
• The Bitcoin Company also has a more lucrative referral scheme haha.
• The advantage of Bitrefill is that it allows me to buy a higher amount of the gift card I want. The Bitcoin Company lets me buy at most $15 worth of the food takeout voucher.
• I wrote a comparison article if you are keen to read more: #541208

You have worked out a way to get your btc off of SN.
I am kind of lazy, my balance slowly creeps up but I dont know if I really want to spend it on a gift card.
My mindset right now is just to keep it on here.
SN will let me keep my balance here, right?

Bitcoin Company is the one I use more, both for its available brands and satback rewards. Bitrefill is nice though, I use both liberally depending on what needs buying.