Are online giveaways even worth your time? Well, that is a relative question I guess, but seriously do any of the online giveaway sites even actually give anything away for free? How could they do that right?
Most websites that offer any sort of free online giveaways, have some type of a catch that you will have to overcome or accomplish in order to get what you're after. Whether that be in the shape of a survey you will have to fill out (which usually turns out like 10 surveys) or a tit for tat situation where you receive the "free" online giveaway if you get something else first. Unfortunately this is the grim reality with giveaways generally. If you are looking for the best app for picking the a winner on Facebook and Instagram then you can browse the web.
Tons of different blogs offer their personal giveaways. Usually they have the items sponsored by someone, and then give them away to people who follow their blog. It is good advertisement for the two parties involved, and if you are already a member of the blog, you get a chance at it until others know about it.
Searching different blogs and the giveaways they offer can be very worthwhile at times, and extremely time consuming at others. There is not really a better or worse between blogs and websites, just different types of giveaways.