For now then, could you do a run on your system and compare the three.
i like furmark because its got a simple 30 second test, and anyone can run it very fast. it gave higher wattages than 3dmark did, so to me that means its LESS limited.
heaven is a bit more complex since you can change off the default settings, and it takes longer.
Well what I ment with limited by drivers is that for an instance Nvidia drivers can detect furmark, and will downscale the GPU clock to prevent the card from using too much juice and potentially damaging itself. This isn't workload related but purely furmark related as that program specifically gets recognized.
I would also argue that even if programs like furmark can coax the maximum out of your card,; the result isn't really all that relevant, much like the maximum amount of GFLOPS isn't that relevant. Sure your card might have a higher theoretical peak, but more often than not this only relates to real world workloads in only a very rough way. Edit: There are no games that only let you play around with a furry ball/symbol/couple of letters.
I agree with though though, it really is simple to run, but even that simpleness has its downsides, as in 30 seconds your card probably won't really heat up all that much and as a result might give different results compared to a longer run of some other(or the same) benchmark.
Heaven, like 3dmark also has a default preset anyone can run(I think for free aswell?) It wont take nearly as long however.
I'm also open to other suggestions, but I stand by my advice against furmark
