As you'll see on the comparis.ch tables in english returns on the investment product for 3a aren't great for the last few years with most LOSING money.

For the moment it may be worthwhile sticking to cash, although unlike the Pillar 2 there isn't a minimum return specified in the law. This is one of the aims of the fair-rente campaign which may lead to a referendum via popular initiative.
(To say nothing of the returns on the state Pillar (AHV/AVS).

In addition it's possible to contribute to a life insurance product (with or without investment, personally I'd stick to a term-life and I work in insurance) as part of a Pillar 3b. These premiums also tax deductible.

A benefit of the Postfinance online system is that through their internet portal you can keep an eye in one place on how your funds are doing. They also pay interest every 6 months, not just once a year like a lot of accounts. With a little change after 1 fully years contribution the yearly fees are waived for your main account (currently 7500 for standard banking).