I'd keep the unattributed 38-D 3-legged buffalo. J/K. I voted for #1. It has the best eye appeal to me. TC
If there was an option to "Sell all 4 and use the money to buy a nicer/better coin," I'd vote for that. In the absence of that option, I would vote for #2. Here's my "logic": #1 Has a nice little rainbow on both sides, but either a scratch or a planchet issue on the reverse. Toning is selling right now...so I'd capitalize on that. #2 Has a better strike than #1, no noticeable flaws. Not the highest grade...but IMO more stable than #1. #3 Again has rainbow on both sides, but not a super high grade. Would capitalize on the toning as per #1. #4 Is readily available in MS67 and MS68...so unless it was an RPM, I'd sell it as well.
I think you must be confused. There are no Buffalo nickels of any date "readily available in...MS68". NGC has graded a total of 26 and PCGS a total of 10 Buff nickels from 1938-D. The last NGC example at Heritage brought $3,400 graded MS68-star. The last PCGS example in MS68 sold for more than $16,000.
I will admit to not looking up population numbers before making that statement. I was just trying to say that an MS65 1938 D would be easily replaced, and in higher grades. Also...not all of them have been graded. EDIT: Confused, no. Temporarily lazy or distracted, yep. Cards are losing to the Cubs and I've been photographing coins for about 4 hours today.
Replacing a piece of plastic with a coin in it with a higher number on the label doesn't always equate with a better coin. Because something is replaceable doesn't seem a good reason to get rid of it...
I do believe I gave my opinion of the question asked with the information given... And I didn't say that an MS67 or MS68 would be a better coin (although, playing devil's advocate, all variables being consistent, I'd much rather keep the MS68* than an MS65 any day...) I would agree with your point that "better coin" doesn't need to match up with "higher grade on a slab."