The person you're responding to already mentioned variations in pronunciation. There's also the problem of homophones. Then there's the even bigger problem of reading speed. You can comprehend a lot at a glance with characters, which you can't do with pinyin due to homophones. And the biggest problem is losing access to existing literature. While the 繁体/简体 gap can be easily overcome, at least for reading, the character pinyin gap is pretty much impossible to bridge.