I just made this same choice last week. In light of the elections & my pocketbook, I figured there would be no better time than the present to get a semi-auto rifle. I could think of 4 or 5 reasons I might want or need one... plus I may think of more reasons after it's too late
Here were the pros and cons for me:
AR - Pros
1. More likely to be banned than the Garand
2. 12 years (and counting) in the Army makes me comfortable with handling
3. Assumedly widespread availability of ammo for the foreseeable future
4. High capacity, detachable mags
5. Modular
AR - Cons
1. Smaller caliber
2. Doesn't perform well dirty (as I found out in Iraq)
3. Expensive
Garand - Pros
1. Battle tested/proven in severe environments worldwide
2. Larger Caliber
3. Relatively inexpensive (through CMP)
4. History, beauty, etc
Garand - Cons
1. Heavy & long
2. Clips vs. Magazine (a con mostly because of capacity)
3. Cost of ammo (non-milsurp)
In the end, I chose the Garand for the following reasons:
In caliber, .30-06 trumps .223 because: 1. penetrating power through ______ (fill in the blank) and 2. the minimum caliber for deer hunting in KS is .243 (and I would like to hunt with it). There are a lot of good arguments on both sides as far as capability of the two calibers against human threats, so that didn't really play a part in my decision. They have both been effective in combat.
Concerning the round capacity... I justified going with 8 rounds vs. 20 (or 30) rounds because I figured that if I have to use it for armed defense, I will likely be defending my street corner or something like that... not clearing houses, reacting to ambush, etc. For home defense (i.e. inside the house), I have a shotgun (handguns as backup). When guarding a "checkpoint" (read "neighborhood", in the case of a Katrina / LA riot scenario), eight .30-06 rounds through an engine block should be plenty to stop an attaching party & surviving general melee. Bottom line, I think 8 round en-bloc clips are sufficient for defensive applications. Obviously, in an offensive urban scenario, my choice might be different... I just don't envision myself in that scenario in my civilian capacity.
I know the likely soon-to-be AWB is more likely to effect AR's, but since I'm limited right now to picking only one, I think the Garand will fill most of my requirements (except "plinking" perhaps... but that's what 22LR is for). Also, even if the next AWB doesn't target Garands, there's not an unlimited supply. Sooner or later, CMP will run out. I've also heard that in the mid 80's, you could get a Garand from CMP for $200... now, a SG M1 is $600. At that rate, in 20 years it will be $1800 even if they do have an inexhaustible supply.
I'm not familiar with the Garands shooting capabilities while dirty, but I know it worked well enough in the waters and sand of Normandy & Iwa Jima, the snows and cold of Korea, etc. etc. I also know from personal experience that it took a lot of time and cleaning to maintain an M4 in the dust and sand of the Middle East & North Africa. Worse case scenario, the M1 is just as prone to stoppages and they are even. Best case, I guess, is that the M1 is a little better.
My bolt action hunting rifle is .30-06, so that's one less caliber I have to stock (especially with an adjustable gas plug).
Ok, didn't mean to write a book. This is the reasoning I used to eventually decide on the Garand. Of course, I would like an AR or two (or a dozen) ideally, especially since that is the platform for which I've received the most training but tough times call for tough choices...
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