Not exactly on top but.. I owned a new X5 for a little bit. I knew I made a bad decision a yearish in when it was having electrical issues (resolved under warranty) but when walking to the service desk noticed finance offers to help pay for your BMW repairs.....

 

LC500 hands down. And this is coming from a very strong former BMW fan/owner.

LC500 is one of my dream cars and I am extremely picky. LC500 is just about perfect as an ICE car can get. The interior is about 200x better than any BMW. The exterior is unique. The quality is top notch. The V8 sounds great. Also go with the convertible if you want fun.

 

The Z4 is a very good looking car. I imagine it would be similar to driving a MKV Supra as it’s the same platform. I imagine they’re quick and nimble. I really like these but haven’t driven one myself.

I think the LC is blast to drive. I don’t own one but I drove them a lot and it always put a smile on my face every time. I’d go with the LC myself as the convertible is absolutely stunning with the top down or top up.

 

LC is way more expensive and luxurious than Z4, but Z4 is definitely a more capable car from driving perspective. The acceleration & engine response, transmission and chassis are all better than LC. However this advantages only matters for track driving, it's like comparing a BMW 850i and M4: one is more luxurious and one is more race dedicated. So to answer your question, it really depends on what car you have driven and compared with. My last car was a w205 C63S coupe and that thing just rides too harsh, and I'm never going to utilize its whole potential without a track. Is LC convertible as sporty as a C63? No. It's actually quite slow in today's standard, but it's the right level of comfort/luxury/sporty for me. But if you compare LC to any non-performance sedan, it's a much sporty car.

People want different things for their cars. LC is loud and slow (slower than my X5), rare to see, eye-catching inside & out and comfortable, which is exactly the kind of car I want, and that's why I bought a LC. And personally, I cannot justify buying a Z4, as it doesn't have v8 rumble, drives excellent but you won't need it if you don't track, looks hideous inside & out (totally subjective). So think about what you want the most, and get the best car that fits your need.