Talking like BIP 17 matters anymore is a complete waste of time. Gavin is the lead developer and he has locked BIP 16 as the solution.
Gavin is the lead developer of one client. This is not about clients, this is about the protocol.
There have been no serious technical or security concerns over BIP 16 which would make it inferior to BIP 17. Comparing these two seems to be like comparing apples and oranges.
Actually, there has been one serious bug that resulted from the BIP 16 patch, and changes so many different things at once that it's quite possible it could create security or other bugs. BIP 17 has no serious technical or theoretical concerns, just "what if there's already a bug in the current code?".
Reality is that one large pool and a bunch of small pools are already voting for BIP 16. Only a week from now another large pool will add its support to BIP 16, this is confirmed. I think there are some small pools that are adding their support soon as well.
Reality is that one large pool and at least one small pool are already voting for BIP 17. Another large pool plans to add it as soon as possible, probably within the week.
If you have doubts over BIP 16, the only thing to do right now is to help test it.
The problem with BIP 16 itself is in the protocol changes. While it's possible to debug the client's implementation, that will never fix the protocol-level inconsistencies. On the other hand, there has been some talk of using transaction version 2 to implement BIP 16, which could result it in being made somewhat consistent. I hope something comes of this, and I plan to Withdraw BIP 17 if it's a sensible protocol change, despite the potential implementation risks.
Trying to vote for BIP 17 right now is a complete waste of time and effort and it will only make the transition to P2SH via BIP 16 less smooth. I suggest supporting BIP 16 and then helping to test it more. Finding serious issues in it is the only possible way that anything else will get implemented. The "burden of proof" in this case is with everyone else, not Gavin. He has a solid solution that works, either prove that it's bad or start supporting it. Preferably do the latter and soon.
This applies just as much with BIP 16/17 inverted, except that unlike BIP 16 (due to its complexity), BIP 17 is easily proven to be "probably good" by any C++ programmer.