We don't know much, but for now, I'm going to vote for the after-tax contribution in the 401k. Here's why.
1) The savings plan is unsecured - they promise to pay and they probably will, but if they don't, your money is gone. The 401k, on the other hand, is yours. It will be yours even if the company folds or gets sued (think big - like the BP oil spill).
2) You get the match if you use the 401k or if you use the savings plan. The 401k is safe, the savings plan probably is, but may not be. What benefit is there to use the savings plan?
3) If you put the money into the after-tax 401k account and roll it out to Roth IRA, you do pay taxes now, but you control when you pay the taxes. If you put the money in the savings plan, it will all come out to you in a lump sum - you have no control over it and your tax rate could be quite high that year.
I have seen the earlier post that doesn't advise after=tax contribution.
Not sure what this is about. Generally, after-tax contributions are considered to be a really good thing. There can be some complexities about rolling it out, but they are not insurmountable.
I suppose if you are in a really high tax bracket, getting more money saved in a tax-deferred account is a good thing, but when it all comes out in a taxable lump, that might not be a good thing.
I'm curious about what kind of plan this is and how it is allowed by law. Is there some official name or a number or something? Could it be some kind of 457 plan?