The 3GS effectively has better hardware than the iPad 1.
CPU, RAM, etc. are basically the same, but the iPad has to drive about five times as many pixels. Thus it effectively has much less RAM, an underpowered CPU/GPU, etc.
It's an odd and unintuitive situation, but despite being newer than the 3GS, the original iPad is ultimately a less powerful device, when it comes to which apps and OS releases it can support.
I'm sure Apple could support iOS 6 if they wanted to, but I imagine they decided that it wasn't worth the tradeoffs (e.g. poor performance, RAM available to apps, resulting stability or lack thereof).
CPU, RAM, etc. are basically the same, but the iPad has to drive about five times as many pixels. Thus it effectively has much less RAM, an underpowered CPU/GPU, etc.
It's an odd and unintuitive situation, but despite being newer than the 3GS, the original iPad is ultimately a less powerful device, when it comes to which apps and OS releases it can support.
I'm sure Apple could support iOS 6 if they wanted to, but I imagine they decided that it wasn't worth the tradeoffs (e.g. poor performance, RAM available to apps, resulting stability or lack thereof).