Some one with more expertise than me might have a better answer but the more solid the back wall the more consistent and repeatable your shot will be. There is less of a chance of creeping back into the valley of the draw cycle or pulling through the back wall if there is a more solid back wall. It usually promotes a more consistent end to draw cycle and a repeatable place to start firing method.
And while a kisser can help with that repeatability, the shooter can also start smooching his lips and contorting his face to find it, not as repeatable.Some one with more expertise than me might have a better answer but the more solid the back wall the more consistent and repeatable your shot will be. There is less of a chance of creeping back into the valley of the draw cycle or pulling through the back wall if there is a more solid back wall. It usually promotes a more consistent end to draw cycle and a repeatable place to start firing method.
If your bow has less than 70% let-off, cable stops can provide a back wall that is solid enough.
But if your bow has 80+% let-off, you pretty much need limb stops in order to get the back wall solid enough to be consistent when using back-tension.
Sounds like you should just shoot the Merlin.The best shooters use the hardest back wall possible. I spent over 50 years shooting longbows, recurves, and round cams on compounds. I shot my best scores in the 80s and 90s shooting out of the center of the valley. In the last ten years, I have shot bows with a solid back wall, 75% let-off and a very short valley and I hate it. Pulling against the stops makes my bow wiggle.
I thought it was my age (69) causing the shakes. After reading an article about Merlin bows on AT, I took my old Merlin out and shot it a few days ago. What a pleasure. It held like a rock. Then after shooting the Merlin for a couple of hours, I decided that I better practice a bit for the State Blue Face I was to shoot the next day. I took my Hoyt and had a hard time trying to hold still in the X ring and the bow kept trying to pull forward while I aimed.
I continued to have trouble aiming the next day during the State Indoors. I looked like I was having seizures trying to hold still and I could feel the man behind me trying not to shoot at the same time as me. My point is that I should not shoot any old bows no matter how good they feel because it takes a few days getting use to the new bows again. I love shooting out of the middle of the valley on a bow with a 65% let-off and a long valley. I have just bought a new to me PSE with Drive Cams and hope that it is a little easier to hold that my Fuel Cams or Mini Evol cams