I'd say that the most important non-subjective thing to look for is support services. Basically length of warranty and whether onsite visits are provided in case anything goes wrong. Oh, and some companies provide accidental breakage warranties, which given how laptops are treated is quite a good thing.
Subjective things to look at is ergonomics (maybe it's just me, but I can't stand most modern laptop keyboards and touchpads).
Specific branding stuff is hugely subjective... I personally like Thinkpads because of their red mouse pointer thingie and because their service centre is still remarkably competent (well, their techs panic if you speak English to them over the phone, but they are still pretty good). Oh, and because you can also carry spare batteries for them, instead of the bloody stupid trend of having batteries built into a solid aluminium chassis (shiny, pretty, but hard to service and impossible to keep away from power points for long periods of time... and if you're doing serious number crunching that burns more power than web browsing).
Spec wise, if you are looking at laptops, it doesn't matter. Just get something with a quad core i7 mobile processor (I assume that your software is capable of utilising multithreaded processors), a crapload of RAM and an SSD. Once you hit those three points, the brand won't affect performance.
Edit: And i7 over i5, as the i5s are dual processor only.
So unless you've got some compelling reason to move away from your Thinkpads, I reckon you're onto a good thing already.