Asking "what is the best suspension" is like asking what the best beer is.
It's whatever you have in hand at the moment or what you can afford.
As was previously mentioned 4" is good. But really, if you "never" take it off road what are you looking for? A boulevard cruiser? In that case anything would work because all you want is a bigger tire and rim combo. Use a body lift, cut some metal and you can squish 39's under the fenders. Just don't hit any large bumps or climb any curbs. If you reckon you will succumb to the thrills of off-highway usage then go with a suspension lift. But leave the body lift off.
If you want to keep the performance on the cheap keep it stock height to 2" and don't change tire size. For comfort, the flatter you can keep the springs the better. If the springs on there now are drooping just putting new stock height springs on it will raise it about an inch or more and improve the ride quality many times over. Any spring on all of these trucks need positive arch to some small degree. The moment they sag to absolutely flat or point up they are gone and so is ride quality. For the research keep in mind that more equals better. More leaves equals better ride, especially in the front. You can get a 2 leaf spring pack for less than $100 but the truck will ride like a rock. For example, take a flat 1/4" thick crowbar and bend it, now take a 1/4" of built up layers of foil and bend them. Maybe not the best of examples but you get the idea. Thick is stiff, thin is flexible. It takes more steel, time, and labor to make a flexible (softer riding) spring carry the same load however so that spring will cost more as a result.
And beware the trick of many suspension makers selling you a spring then including a load leveling spring (add-a-leaf) to make up the difference. This is poor marketing at best and a rip-off at worst. All the extra leaf does is take up space and stiffen the ride. Using a zero rate spring (the politically correct term for lift block) will do the same thing and do it much cheaper. Just don't put a "block" taller than 1/2" under the front springs.
If rear lift blocks were bad then truck manufacturers would have stopped using them decades ago. It's a cheap fix and it's safe (in the rear). Not so for the front axle however.
My 6" lift was springs in front and 2" springs in the rear with the stock 4" blocks and I used that for everything from mud to mountains. However, for me it was a cost issue, it is (was) also much cheaper by hundreds of dollars. And since I put the suspension and tires on new (all at the same time) those couple hundred dollars meant a lot.
As a side note, when I say I put the suspension on I mean the shop that did the work. I was living in an apartment in a ski resort in Colorado at the time so I had no way to do the work myself (safely- as in being ripped off). So the good folks in Carbondale got my truck and installed a Trailmaster lift with traction devices, M/T Tall Baja bias belted 39x15-15's on white wagon wheel rims and Rancho shocks, a twin tube stabilizer and the associated lifting necessities for the front steering such as a dropped pitman arm and raised steering arm and lowering the t-case. Pretty standard fare for the day. The bill out the door back then was really close to $1800. I wouldn't even be able to come close to the same thing for less than $2500 today and the vast majority of that cost would all be in the rubber. And that's if I did all the work myself.
Good luck with whatever you decide on. It's all fun.
