So is the lack of much suggestions of Apple laptops due to cost or other issues? If someone just wanted to build a platform to replicate pretty what the Looperlative LP1 does, and if I had Steinberg A/D converters, and money were not particularly an issue, would the Apple be your suggestion?
Andy not Butler
You might want to look at ThinkPads and IdeaPads from Lenovo as well - they seem to generally be well regarded (I've seen this discussion come up a lot on the GearSlutz music computers, where they're definitely most concerned with issues of latency/etc. for running their DAWs).
Probably one of the biggest things you need to identify is exactly what you'll be doing, and how much CPU and memory that's going to take - it should give you a better baseline over what you'll need.