Google Analytics can do most of what springmetrics does and none of what the SEOmoz tools do. They're quite different pieces of kit... for SEO, I mean not just measuring but doing, there's no way I'd trade SEOmoz for anything, let alone something that can't do any of the stuff I need it to.
The Q&A alone on here is worth the spend, then you've got the crawl errors, OSE, a whole host of other tools... and that's not to mention the stuff they're working on at the moment to come out soon. You'd be mad to swap out, especially as the two options are miles from "like for like" in terms of what they do.
Spring Metrics = Analytics tools
SEOmoz = SEO tools

