Everyone's so fast on 4x4! I can't seem to get below 1:25 ave. So many ppl around the same speed as me on 3x3 are around the 1 min mark on 4x4. I wonder what it is that im missing. Most likely practice but im sure my method is a part of it.
As I'm about 2 seconds slower than you on 3x3, but about 5 seconds faster than you on 4x4, I feel I'm in a decent position to answer this question?!
We had a little exchange a while ago about how looking further into 3x3 solves during inspection helped me drop a good 1.5 seconds off my average (over a few months). I don't think, with 4x4, it's
so much about inspection, but efficiency and lookahead during F2C is somewhat useful. I've found I'll always know at least how my first centre is being built completely during inspection, and where the first bar of my second centre will be formed. I'm assuming you already do this, though!
As I say, I don't think it's SO much about inspection with 4x4, and the biggest kick in the teeth (for me) is always first 3 cross edges, and I think it's where I make up a little time. The key to cross edges really is lookahead. If you can spot something to get you going during F2C, you're on for a winner, then (like 3x3) it's about not going too fast. This is the hardest stage of (the Yau method of solving) 4x4, so I guess we should all be practicing it in the same way as we practice F2L when trying to improve on 3x3, but nobody makes much fuss about it. At least not to the extent that fuss is made about F2L on 3x3...
Do you use half-centres? J-Perm (can't remember his forum name) recently made a good video on YouTube about looking ahead between the last 2 half-centres, which helped me knock a little extra time off. Half-centres in general are great for L4C.
I'm assuming your edge pairing is solid, and your 3x3 stage will clearly be good. I think a lot of people neglect cross edges, and we should all (me especially) probably dedicate a lot more time to it if we want to improve 4x4.