I used a LaCie Porsche drive with my G3 iMac for several years. To be honest, I was surprised that the iMac's own hard drive continued to perform like a trouper despite the computer being a real workhorse for a good six or seven years. The LaCie external performed fine too, though I would sometimes have difficulty getting it to 'mount' on my iMac's desktop.
A friend had several external LaCie d2 drives and a couple of them failed.
With my current MacBook I looked at various web feedback, at reviews, and then went for an Iomega portable drive to plug into it, because the price was good, the storage was sufficient for my modest needs, it had a USB 2 and Firewire 400/800 options, and there was sufficient positive feedback to reassure me. So far so good!
I do like LaCie's SilverKeeper software. I've grown used to it and I now use it (a newer version) with my Iomega drive. I believe you can download it for free.
Good luck with your purchase.