For grenades and bombs, Goblin is the best choice. However, the best advice I can offer you is this: If you are good at "point and click" with your mouse and have no trouble always hitting the target you intended, go with Goblin engineering. If you are a keyboarder and use your tab for everything, go with Gnomish. Reason behind this is that Goblin bombs require heavy use of the mouse, and some people just don't play that way or aren't as skilled with it as others. If you think you are, then goblin is a good choice.