Well, I can vouch for mi300 on overall review.
let's start on the cons.
Indeed it is not very well build, I have to say that it has squicks here and there. And of course the galaxy mini will have more RAM then the mi300 but that's the only cons that I know of.
Pros? compared to mini? a lot

First the resolution, mi300 have a HVGA screen (320x480) on a 3.2inch screen, means it has a ppi (pixel per inch) density of 160 ppi. Note that ALL application requires at least HVGA screens, and above to run properly, in Galaxy mini, you'll have a QVGA resolution, and believe me, not all application support that resolution, engadget for example. Plus mi300 have a crisp display in text and image compared to the mini, the mini as the vid shown is more pixelated so text and image won't be as good as the mi300. In terms of CPU and GPU, both uses the same Qualcomm msm7x27 and Adreno 200 GPU. In terms if it's easily "spoilt", depends on the user actually, all smartphone are fragile,samsung included, the mi300 although are a little bit durable because of its pure plastic built

Although screen protector is a must, same as other touch base phone out there.
Overall I'd say if you bought the mini, you'll be wanting to trade for the mi300, if there's any since it's discontinued. Or you can save up 200+ more to bought a better phone, the Ideos X5 like Rudd said for example.
i read that csl have a promotion in bukit jambu mall this sunday, i will buy it. Haha, so great.