I wouldn't buy stock in a Brammo IPO. I don't understand how IPOs operate and I don't gamble with things I don't understand at all.
I think Brammo has a better chance of being around in 10 years than Zero, but a worse chance of being around in two years. Brammo is making a bunch of long-term plans that will hopefully serve them very well (partnerships with Flextronics, Polaris, SMRE, HKPD) .. but they have to survive in the interim.
To date they have successfully brought a single product to market, the Enertia in 2009. Brammo says Enertia Plus and Empulse should be out very soon .. we continue to hope.
Speaking very generally, I believe the E+ and the Empulse R are better values than the 2012 Zero S bikes .. but I don't know how many bikes they will sell. They're being released much later and much more expensive than expected in the tail end of a year where Zero has already captured a good number of sales. A 2013 Zero refresh is surely forthcoming, and Zero has enough advance notice to ensure its bikes are competitively positioned with respect to Brammo.
I would guess Brammo and Zero both are burning around $10M/year in operational expenses. Brammo's recent $13M funding round may buy them a year. An IPO might buy them more time. But eventually both companies have to start turning a profit based on sales. Selling 200-400 bikes/year is not going to keep either of them afloat.
Answering the subject question.. I would rather buy a product from an EV company than stock in an EV company.