As @AKA_Ben said, Notifier does not require Winterboard. To me the difference is simple. If you want/like the fancy icons on the lock screen in addition to the little status icons plus support for lots of other SMS programs (like BiteSMS, SwirlySMS, etc), go with Status Notifier.
If you want to keep it simple and only want the status icons, Notifier is the best choice. Personally, I prefer the simpler/cleaner approach. Either way --- no background program is running like pre-2.0 versions.
BTW: I'm not 100% convinced they don't add some kind of additional processing requirements (or prevent deep sleep modes, etc) and thereby slightly reducing battery life. That addition, if any, is relatively small for sure

I can't provide any quantitative analysis to support either position.