I love my rezound and would recommend it to anyone. Most underrated phone of the year by far. Only complaints I have are bloat and superficial. Bloat will be able to be disabled with the ice cream sandwich update.
The biggest difference you will find between them is that one is htc and one is LG. LG makes solid products, but it's not htc. There is quality in software and hardware that will not be quite the same generally. That being said, you might like the spectrum better, and if you do great, but the rezound is probably a better choice imo.
O and if you have aspirations to unlock and root, then I could be wrong but I don't think the spectrum has much of any dev support.