Since you used "SVG animations" in your question here i'm assuming you're asking about native SVG animations(SMIL) here.
Here's what I would do.. For simpler transitions, use CSS Animations for sure. Use and manipulate SVG elements with CSS for anything extra, Basically anything that is doable with CSS, Do it in CSS.
For complex situations however, Go with SMIL.
Simply because SMIL is capable of animating properties that CSS just can't currently animate – such as path data properties, for example.
You can do more awesome things with SVG using a library like snap.svg which is like jQuery for SVGs
Native SVG animation features are also being ported into CSS. so there are good things ahead :) Here's a nice guide that you can use to achieve them: css-tricks.com/smil-is-dead-long-live-smil-a-guid…