Reinz is $10....OE MB is $20, which should I go with?

I have ordered both the regular crank seal and repair size seal just in case.

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Do I NEED to remove the belt tensioner assembly? I cannot tell if it actually gets in the way or not?

Also where can I find one those locks inexpensively?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k