Rounded edges => better "feel in hand". That's a concept I hadn't considered
Kent.
When you mention "the Defender"...are you referring to the (older) Defender-36W or the (newer) Defender-50W? (or...both...)
Have you seen the pictures of the "new" iStick 60W TC? Does it look like it has the "rounded edges" that you're talking about?
http://www.angelcigs.com/eleaf-istick-60w-tc-box-mod-black-authentic.html
Gerry,
The rounded edges are important to me by the way I hold mods. And as we've seen not everyone holds them the same - see the kent, katya, andria posts above
I hold it like the top picture in one of katya's posts except in the left hand...
Little itty bitty mods under $100.
- a fist - full contact all around where the pad of my index finger fits perfectly on certain models. If the circumference is too small - like the istick 20/30 or the stick mini, then I have to remove the index finger from the 'fist' and fire with the tip of my finger. If the circumference is too large - then the opposite end from the fire button is more toward my thumb knuckle like I'm forming a C with my hand rather than a fist - as in the Joyetech VT.
The main factors are width and depth. Phil-like nit pick
Kbox mini (subox) 39+22 = 61mm - perfect for me.
Defender 25/36W 35+23 = 58mm - ditto
Subox nano 38+22/18 tapered = @ 56mm - goes toward the knuckle rather than pad
istick 30W 32.5+21.1 = 53.6mm - have to remove from and hit with tip of finger
Joyetech VT 47+25.5 = 72.5mm - too wide
Joyetech VTC mini 38.2+22.2 = 60.4mm close to kbox mini BUT the squared off corners makes it 'different'

IPV D2 - 38+22= 60mm - (also rounded) closest to kbox mini
istick 50W 44.8+22.9 = 67.7mm - too wide for me but the rounded corners helped.
istick 60W - 38.5+27.5 = 66mm - might be ok but also might open up the fist a bit. Also prefer the 82-85 height vs. 90+ (istick 60, most ipv's (except d2- l=76mm), but not as big a factor as the actual grip.
A main factor on depth is what fits it. For example the ST nano 18mm of course fits the kbox nano perfectly. And the GS Air M (fav) is 19mm so there's a .5mm hangover but it is not that noticeable. A 21, 22, 23 would overhang too much for me. The aerotank mega fits the Defender perfectly - a bit of overhang on the kbox mini. The GS Air TC/Tank also fits the Defender but a bit of overhang on the kbox mini, however it's flush with the vtc mini?? +
And yes, the rounded corners are important to me for the reasons above - and it's the main 'interface' for us (along with the drip tips - thank goodness they're replaceable :- ) - so unless the mod has maintenance or other problems, it's a main factor for me. Again, if one doesn't hold the mod in the manner I do, then other things may be 'main factors'
Weight was a factor for me not liking the MVP 2.0 - however.... that was coming off of 4 years of vaping eGos exclusively (well - including a reo mini :- ) so the difference was great. Now with box mods, it isn't the factor it was then, although the Evic VT is a bit hefty and some of the other innokins I've handled. The ijoy is both big in size and hefty - 2 batts, but the kanthal TC was what interested me - hopefully there will be minis in that format.
Here's the ijoy next to the kbox mini and vtc mini.... the ijoy is about the same size around as the Joyetech VT and a bit taller.