I got an Sx mini ml class yesterday, and i have to say I'm very impressed, battery life is epic, build quality is top notch and feels so comfy to use. The Radius has a lot to live up to, if it does ill be a very happy vaper on Christmas day
I have the SXmini M class, and had an S class before that. I wanted basically the same mod, only with temperature limiting ability. It's a fine mod - really well built (but has a "handmade" list of imperfections), great display (nothing beats it IMHO, not even the Radius), very accurate, very comfortable, and very heavy (a negative for some people). I really, really don't like the look of the newly designed ML class, and would wrap that thing in a silicone sleeve right away - just my personal opinion. I might look into getting the SX350Jv2 modders board and upgrade my M class (voiding the warranty, of course, but not something that concerns me much). Being a Chinese company however, I dread if I ever needed to send it in for service.
The Radius is a different beast. You'll find you hold it differently than the SX. Not better, not worse, just different. It's much lighter, charges faster, is better built, about 1/4" shorter, has better support, and will likely outlast the SX 3:1. It's like comparing mechanicals - they're all metal tubes that hold batteries, but the designs are so different from one to another (just talking about the good ones that you have no complaints about).
Battery life really depends on the battery you're using. You can work out the math, based on the efficiency of the mod, but in reality you won't notice any difference. Everyone here who is impressed with the battery life on the Radius says that because they were using an 18350 or 18500 with their P2/P3, and really never tried an 18650. The logic is simple - at the same wattage, two mods will use the same amount of battery power, give or take a few %, which is really impossible to notice without tracking puff counts and draw times.
I really have to give the Radius and SX mods the top two places in the regulated mod world, and that's above other mods using the SX chipsets, because they get different firmware than the SXmini mod. It's like owning both a Porsche and a Mercedes - they're both good, but very different from each other. I've been using the Radius exclusively since I got it - likely because of "shinyitis". I wouldn't want to give up either one, but again, expect the Radius to be working long after the SX dies.