To be honest, they're both pretty reputable brands. I'm not a huge fan of Acer's 15.4" widescreen laptops.. but the 14" 3627WXMi is an attractive deal, and the build quality seems pretty decent. Plus to assert integrity, both companies include the standard 1 year limited warranty on the machines, extendable to 3 years. If you wanted to do that, just ask the salesman there, and he'll extend it by two extra years for a cost of $189, refundable within 7 days. The warranty slip (regardless of if you extend it or not), is present on your tax invoice. In other words, your receipt is your proof of eligibility for warranty cover, so don't ever lose that, even after the returns policy date has expired!
And just incase you buy one of those machines and don't feel satisfied, you can return it within 7 days to any Officeworks store, with your receipt and all original packaging. Oh, and one final thing salesmen often forget is that when you buy those laptops, you're entitled to a special price on Trend Micro Internet Security OEM ($50). This includes the firewall, anti-virus and all the other bells and whistles. These laptops should only include a 60 day trial version of Norton Internet Security, so yeah, might be worthwhile to futureproof yourself with another one unless you have one already.
By the way, if you're still after the L20, I'd grab it soon. Our suppliers are running out of stock fast.. my store ran out a week ago, and we don't expect to get more of them in soon. If you go to your nearest store and they tell you it's out of stock, get the guy to find out on their SAP intranet system which other stores have it. Then get that guy to 'raise an STO' (essentially just a store transfer process), and bang.. laptop arrives near you in 2-4 working days, unless you wanna drive.