There are pros and cons to both designs. i have seen both dog and mesh shifter work on a first robot. Efficiently team 45 (technokats) has done dog shifting and 180 (SPAM) has done mesh shifting. personally i am supportive to both shifters. but mesh shifter is probably easy to build (i am not an engineer YET). but i am sure that Andy Baker from 45 and Gary Dillard from team 180 can tell you about both shifters...
