I have a afe twisted steel on my 4.0. I replaced a cracked cheap aftermarket header that replaced my factory header.
I don't know about the 4 cyl version, but the 6 cyl is definitely thicker and better built. The one I have is all stainless steel, tig welded, bends are nice and smooth, ports look good, flange is nice and thick and lines up good. You could tell a noticeable difference in the weight of it compared to the cheap one. It weighs a lot more cause there is more metal there. Tubes are noticeably thicker. I could tell a ever so slight difference in performance Vs. the cheap aftermarket one.
I bought mine about a year ago and it looks like prices have went up a good bit. I got mine on amazon for like $385. Looks like they have went up about $200, ouch.
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch. Currently building a stroker.
'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.