Overall, I do better with BJs. I only buy when they send me a coupon or reward. I did get a discounted membership.
Target is great for a standard 5%. They do have the deals where if you spend a certain amount, you get a bonus. But I don't take advantage of those as they are not direct savings on gift cards (you can't usually use the bonus to purchase a gift card.) Others here do use this method, and (I guess) just reassign the savings in their budgets, which works.
So far, this year, I have saved about 27% on $225 in gc from BJs. I haven't gotten any from Target this year yet. My overall savings this year on $1950 in gift cards is around 55%, but that includes using SUB bonuses from two Inspire cards, so it is very inflated.
Last year, I saved about 15% on $575 in gc from BJs. From Target I purchased $100 and saved 7.5% (used cash app bonus once on a $50gc). My overall savings last year on $1425 in gift cards was 13.48%.
I don't include any savings from my cc (Discover cashback or Chase URs earned, for example) in my calculations.