Are you doing a dry start? If so, then blast it with the highest wattage light. (but you need to try keep heat down somehow). If not, both are way too much for a 3g. I'd go w/ a 9w cfl. My high tech 5.5g has a regular 13w 6500K cfl (cost me 3$ at walmart) and that's just perfect. (i have crappy reflectors though.) If you need pics, the link is in my sig. I've been able to carpet HC in that tank. So yeah, you should def be able to get a carpet w/ something like that, assuming you have adequate NPK+trace coverage, (optimally) co2, etc etc.
Yes I'm doing a dry start. So should I try with a lower wattage or stick with 14?