Remember, to understand a fighting style better, especially a more traditional style you have to understand the culture behind it rather than just the sport. Karate, Tae Kwon Do, Muay Tai and Gung Fu (Kung Fu) originated in Asian countries. Most Asians are lighter, more nimble and much more suited to the high kicks, jumps and their specific exercises to increase their strength, speed and mobility. More to the point, apart from muay thai, the others I have mentioned are heavily marketed to suck in cash for ineffective techniques often by under-qualified instructors. Seriously they can go to a martial arts store, buy their black belt, have any stripes or symbols embroided onto it and teach substandard techniques because people think a person with a black belt can fight well...especially when it comes to parents wanting their kids to learn some discipline or how to deal with bullies. A belt means nothing unless it has been earned. However unsuspecting people dont know that and cough up the training fees on demand every time.
I know I have just bashed a few styles in the face here, but I must point out I train in a traditional art however it keeps a few more if its old values (Kyokushin Karate). Look up WKF karate and kyokushin karate on youtube to see the differences and why I prefer training in the latter.
The styles that a heavier person would be better suited to would be things like Judo, jiu-jitsu (Brazilian Jiu jitsu is good fun but traditional is effective too depending on the school it may teach weapon disarms and strikes as well as grappling) If you have no intention of competing you may even consider Akido or Aki-jiujutsu.
While on that, have you ever had exposure to the fighting styles of the Philippines? Kali (sticks) Manu Manu (hand to hand) Pangamont (simplified jiu jitsu) and knives (forget what they are called) all fall under eskrimina - one of the most underrated fighting systems - all are fun and effective.
Remember that competition can ruin an art. Sport and competition does have its place in various styles. Its fun but there are more benefits to martial arts training than just fighting and getting medals to show to visitors when they come over. Most importantly try a few places out and see what you enjoy the most, thats the best way to find out what is good for you and what is not. Remember to take particular notice of the higher grades and advanced students and think to yourself "would they handle themselves in a fight?" If your not convinced, then go somewhere else.
Sorry to rabble on, but after 8 years of training in various fighting styles Ive seen many instructors who give their style and all martial arts a bad name through their incompetence and greed. I hope neither you or anyone else ever have to see what I mean.
Tim