At work my desk is right next to a male co-worker who is both my junior in age as well as position (though I'm not his manager, just higher ranked).

The co-worker I'm talking about is fat, loud and likes to be the center of attention. I don't like those types of people, especially at work, but I keep to myself and just focus on my work. However, this guy is always trying to disagree with me whenever he gets the chance. If I propose a something to the team, he will almost always oppose it. I usually brushed it off by saying that if he has a better idea, he's welcome to contribute - he doesn't.

This leads to today: We have a new employee that was under my training. My coworker trained him for a few days because they are the same age, but the new guy is under my supervision. As we were going through workflows, my coworker started listening in on our conversation and then butted in saying that my workflow is slower than his. This annoyed me a lot, so I told him loudly with the whole team around: "Put your money where you mouth is. You do it your way, I do it my way and we see who's faster". I can tell he was bothered by this - avoided eye contact, saying "Nah, I'm here to work, not to compete", but the whole team knows that I have the highest productivity, and will surely win this bet. Even the new employee told me that he liked my workflow more and he noticed that I was the most productive.

I have been ignoring the coworker ever since I noticed that he was opposing my ideas just for the sake of it. But it's hard to avoid him since our desks are next to each other, and he still greets me from time to time. He's also very talkative so whenever the girls in the office started some discussion, he will join and it will be too obvious to the whole office if I ignore him. They would think that there's some beef between us.

I like this current job because because it's quite easy-going for me. While my co-workers always complained about being busy, chasing deadlines etc... I found a workflow that allows me to chill at work and still deliver double their output. I am willing to put any dickhead in their place if need be. My relationship with the manager and CEO is also quite good, so the only thing I'm concerned about is not making unnecessary enemies.

Do you think I did the right thing? Or perhaps I should have been more tactful? I'm eager to hear what you guys would have done in my situation