I like what you are going for with the first shot, but I think that hte upper middle section is just not defined enough for it to work - especially when you compare it to the colour version. For me I prefer the colour version - though in this the out of focus stem in the foreground is a little more dominating and distracting.
Also the shot looks like you are getting a little overexposing from the light above - next time I would try underexposing possible by a little to try and lose this effect. - shooting in RAW can also help (being able to alter the exposure)
Overall I think you have found a really interesting shot here and with the water drops its really something. You have also got the colours and sharpness ok (I have a feeling the some sharpness might have been lost through resizing and webposting possibly) - but there are a few problems (mostly I think its that stem). I would try carrying a few short sticks and some binbag ties or thread - use this to tie back any bits of plant that are getting in the way (remembering of course to always remove such things after you are finished shooting)
ps = I would be interested in your views of the sigma lens - pm me them if you wish
sorry dont like the top one at all - too much blown hilights
and the 2nd one is much better - but you need to take more care with the focus, it is at least 4 pixels out!! - if you were not a 'no edit person' I could show you - the difference is amazing.
But having said all that I like the composition - well done.
Yes i like the top one too, i think the colour helps keep the detail up as it has been noted that they are a little soft and the bw compounds that, it may also be a little camera shake, were they with a kit lens by any chance, if so they are amazingly good as they are really hard to get this kind of shot from in my experience.