Are you better off with something properly sized? No doubt about it.
Of course weight is an important variable, you can't neglect physics... but as wrong it is to say weight is BS, it is also wrong to say it's the only
determining factor. It's simply only one
- important, tho not the only - factor, as wrath indicated nicely
Mixture of skill level, riding style n purpose (terrain, snow conditions, personal preference), weight - then loooong gap - and then height (only matters for the extremes as mentioned by linville). Charts just can give limited dimensions and should be taken as what they are - references. Not more, not less.
Really think that this calculator is useful cos it covers more than only the height/weight variable otherwise used in charts SnowLifts.com - Snowboard Size Length Calculator
(BTW: radio, if you check that calculator, you'd see that my boards are "properly sized"
. Recommended: all mtn 154, BC 157. I ride all mtn 153/6, BC 156/8. Nothing extraordinary there. The long ones you may have seen in other posts were just demos not available in my preferred size).