To the OP: Similar scenario I just went through on my new SD. I spent countless hours learning the ins and outs of the various suspension types; 4-link versus radius arm, coilover versus reservoir, full deavers versus blocks and so on. I still don’t know squat about any of it but I will share my conclusions all the same.
I assume you will want the truck to ride better than stock on pavement, no problem there with either choice.
If you want to tow and it sounds like you do, I would think the 4.5” lift would be the better choice.
As for 4-link versus radius arm, this is where it gets ugly as everyone seems to have a strong opinion. My belief is that it depends on what type of off-roading you are doing. Serious rock crawling might make a good case for winning the 4-link versus radius arm debate but not by much in these lift sizes. While the articulation will be better on a 4-link, the strength will be better on a radius arm. So if rock crawling competition was your thing go with 4-link but if occasional rock crawling during hunting season, you’ll be more than happy with radius arm.
If none of that helped, then it boils down how you want the truck to look. As someone told me in another thread, be honest with yourself and you’ll get exactly what you want.
I went with the Carli PinTop kit. I added the full deavers and hi-mount stab with 37” Toyo’s. The ride is phenomenal on pavement. What off-road I have done (mild) it has taken it all without a single white knuckle moment. I will get it out for some more serious off roading this weekend I hope. The guy who installed my lift runs a ProComp leveling kit but had his Carli order in before I picked up the truck and ¼ tank missing. LOL Another friend runs Icon 4.5” Coilovers and another just installed a Fabtech 8” lift with 4” coilovers; both are supper pissed off after riding my truck. In their defense though, they both are running 22” wheels which I believe cancels out much of their lifts benefits.
Either way you go, have fun and be sure to get us some pics so we can all talk chit about who has the best truck!