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I use a Kahr P40 and S&W M&P 40 compact depending on clothing and season. Both very reliable and accurate.
The Kahr is less than one inch width and extra mag is thin single stack. The M&P mag is a double stack so it is a little thicker.

Try what fits your hand is my best starting advise. I was "sold" on getting an XD until I went to go buy one and found that it didn't fit my hand nearly as good as the two above. I have smaller hands. That and a good fitting holster (I ended up making my own Kydex IWB) I found are the two biggest factors for me.