Which key of harmonica is more easier to be draw bent?

Hello Jeff. Not one harmonica is easier than the other to learn how to draw bend on. Experimenting with different holes is a good idea though. You may find one of the holes will give you better movement. If you find the 4 draw to be easiest for example, work on that one for a while and then work up the harmonica, using more of the front of your tongue, further forward in your mouth. Then work on the 4 draw again to get a feel for where your tongue is, then move down the harmonica, focusing on using more of the back of your tongue further back in your mouth. It's a process over time to learn how to bend... work hard, but be patient.