Comparing these apps is like, well, comparing apples and oranges. I've had them for different lengths of time. But these four are actually all apps that give you cash back on purchases you make. So maybe it's apples to apples in that sense. From smallest reward to greatest...:
Paribus is the easiest app to set up and forget about. It scans your inbox for receipts from Amazon, Target, and other participating retailers, and if the price drops within a week of your purchase, it makes a claim on your behalf to get your money back!
Find&Save is cool. I'm trying not to spend much money now after a big car repair bill, but I see the potential. Some of the spending thresholds are too high. Costco is at $150 right now. But spending $7 at the Dollar Tree and getting $1 back is pretty sweet. I also understand the "cash dash" aspect of it now. Each offer is limited by time and a maximum number of participants, so it can disappear on you. If you sign up, my code (for that top "Share with Friends. Get Cash" offer) is YM8D. Thanks!
Ebates is another no-brainer. I even shop Target.com with Ebates and use in store pick up sometimes. Please sign up with my link if you're going to join, as I'll get a referral bonus.
Ibotta is a great way to supplement your coupon usage. There are "any brand" rebates as well as some deep discounts for new products and savings on items you may be planning to purchase anyways. Keep an eye out for bonus combinations, as well to increase your rewards. Right now they are offering a $10 sign up bonus after you complete your first rebate. Lucky you! I think I only got $4 or $5. Happy 2016!