If someone is making a choice between a SIG and a Glock, well then, they just simply need to make an assessment of what is important to them, go and shoot the firearms as much as possible, and then decide. Or don't and get them both if you have a chance to.
This is MY opinion. I have all sorts of different makes and models and brands of handguns. All sorts of different actions. I love my SIG's; an old W. German P220, a W. German P245, and a newer P226 Tacops. If someone gave me a Glock, I'd say, "OK, ummm, thanks", and throw it in a tool box or something.
I have a ton of respect for the Glock, and how it changed the firearm industry. First and foremost, what I don't like about the Glock is the fanboy base that never shuts up about it, and the gun shops that never quit pushing them, even when they are not being asked about, or when it is obviously not the best choice for someone.
That, however, is my own biased dislike for the Glock and it's "industry". The truth is I have tried to like Glock's in the past. I do think they are very good handguns, and they function well. But it feels terrible in my hand, and the trigger feels spongy and vague. People say that Glock's "just work". Well so what, so do my SIG's, S&W's, Kahrs, XDm's, Colts, etc... My XDm owes it's trigger system to the Glock, but feels WAY better to me. I cannot open carry, and I am not a policeman. I have to conceal carry. I would NEVER carry a Glock with one down the pipe concealed carry. People say, "well, just don't touch the trigger". Glad you live in that perfect world. None of my Glock owning CC friends will carry their Glock live. I don't want to be trying to rack the slide in an emergency.
Glock's being ugly? Well, to me the long slide versions do look terrible, but the shorter ones don't look that bad at all. I think the G19 for instance looks just fine.
Are SIG's the end all be all? Neh, but I dang sure like them better. I love the DA/SA. I love that they function like a revolver. No safety's to think about, but it is safe. People complaining about the transition? Honestly, I can't believe that the caliber of shooters out there cannot handle the difference between a revolver's first hurried DA shot, and then the dang thing being cocked for you from then on...and that SA is suweeeet!
Glock's may be easier to completely break down, but I would venture to say that SIG's, as well as several other makes, are easier to bring down for a normal cleaning than a Glock is.
As for the thought that Glock's and SIG's are like comparing Ford's and Chevy's, I would have to disagree. I would say it would be a little more like comparing VW's to Mercedes Benz'. They both run for sure...start up every damn time...very well made. There are those out there that given the option of receiving either car would take the VW. I would venture to guess that the majority would rather have the Mercedes. If you have to buy it, well certainly there are more VW's out on the road, they are simply more affordable.