I'm looking to buy a Sora triple crankset. Shimano make two types one has 5 arms and the other only has 4 arms. Which should I get and why would that be a better choice? I'm a slow-ish rider. I'm 50 and speed is not a priority. But I'm planning a long ride in Asia and Africa next year. Which of the two chain-ring types would be a better choice for spare parts and any other considerations? Note: the 5 arm crank has a P.C.D. of 130 compared to 110 for the four arm crank.