I think it is a valid to compare the 30 to 36 as well as to Defender and two Wilson's and Kimber's and everybody else's similar model. They are all designed for the same purpose--concealed carry and all are .45 ACPs. Actually, if width were if "width is the most important dimension for CCW" for you a Kimber or Wilson or Colt might be a better choice (and they include an extra two rounds to boot). And I would suggest that for concealed carry, slide width is more important than grip width--particularly if you carry IWB.
All of that aside, I would suggest there are many factors go into the selection of concealed carry weapon. One of the more important factors is how well the weapon "fits" (talking ergonomics more not size) and its "shootability" which are even more important in a smaller (for most people) concealed carry handgun than in a full size handgun. And both of these factors are very subjective and user specific. In other words, the "smallest," the "thinnest," the "lightest," and within reason, even the calibre and capacity are meaningless if the weapon does not fit you and/or you cannot shoot it well--remember its mission. I would even go so far as to say, again within reason, concealibility should take a back seat to how well the weapon "fits" and how well you can shoot it. With a little effort and careful dressing (and maybe some minor changes in how you dress), you can conceal a lot of gun. Remember, the goal is "comforting" not "comfortable." (I would caveat this "treatise" to say I am talking about primary defence weapons carried concealed--not back-ups.)
Which, too many words later, lead me back to the G30/G36. To me, the G30's grip is "magic," and I have no trouble carrying IWB--as much as I hate to say it, perhaps the "perfect" weapon for me. You really have to hang on to weapons this when shooting .45 ACP (I carry 200 grain +P JHPs) out of these size weapons. The shooter must maintain a very firm, aggressive grip on the weapon (both to insure it cycles and to get back on target).
So, to me, when comparing the two (G30 and G36) the narrow grip of the G36 is a major drawback (not to mention a 36% reduction in ammo capacity). There are people are there who swear by the G36 (particularly in a back-up mode), they are also dedicated shooters who know what they are doing and spend a lot of time doing it (practicing). There are a lot of people who have had some serious problems with the G36 in terms of funtional reliability (hard to maintain a firm grip to insure it cycles?) to just plain being painful/hard to shoot (hard to hold?).
On the otherhand, most people have found the G30 relatively easy to shoot and very accurate (perhaps the most accurate Glock). There are some complaints about the grip width (but a lot of these are people who have picked one up at a gun store not who have taken it out and shot it), and for some, it may be too wide--I have no problem with recommending they look elsewhere (to similar sized 1911 type or the G27). A narrower slide would be nice (particularly for those who beginning to explore concealed carry and/or IWB carry), but for me, it's a non-issue (most of my wardrobe was selected for concealed carry). I like the way the G30 shoots most importantly. I like the way it carries. I like 10 rounds of .45 ACP. And lastly, I like that it is low maintenance (not that I neglect it). I gave up 1911s for it--something I thought I would never do. I'm carry a Glock--and I used to be something of a "Glock basher" (that's not to say I'm really fond of the rest of the Glock line, but that's another thread).