The TD3 MO (Modified) is the version of the TD3, a clone of the legendary Roland TB-303, by Behringer at an affordable price for common mortals, with additional settings and connections, it has good build quality. Now, just because it has these extra features doesn't mean it's better than the regular version. If you are a beginner and don't have any other synthesizers and want to experiment with all these, you don't really need them. If you want to experience the 303 and the acid/rave scene of the 90s, it's better to get the normal version as it has a more direct sound without too much additional distortion effects. I have both and I use the regular TD3 as the main melody and the TD3 MO as the bass because it has the sub oscillator. You can listen to some tracks I play on YouTube