Indeed, keep in mind that they are very different games. Growlanser is a tactics RPG, and DDS is a more traditional RPG (in terms of gameplay, anyway). They're both great, though, and fantastic examples of their respective genres (or rather, sub-genres).
Keep in mind, though, that if you buy DDS, you're probably gonna want to spend an additional $50 for DDS2 (and you pretty much have to get DDS2, otherwise, you don't get the whole story) when it hits in August (supposidly), so, you'll be in for another hit to the wallet come then. Just something to note when choosing.