Ied say you have to try both out, and figure out what way is best for you..personally i like incubators, but some can fail (exo-terra) and others are extremley expensive for a reliable unit (one that heats and cools)..the choice is yours, its really all about personal experience..
I think it depends on what species of eggs you have and the temp in you closet. If you have veiled or panther eggs and the next 8 months or so your closet temps will be between 74 and 78 the closet method should be fine.