Aim for lower end if you have a choice as .... over time....wear will occur. Remember anything within the range specified by Lycoming is OK. Pushrods can be expensive.....and I also found there is slight variation within same part numbered pushrods. Make sure you read the latest lycoming service manual regarding pushrod lengths & selection. Certain families of pushrods are not to be mixed with others in the same cylinder.
Ellis
While researching this a year ago, most folks with tons of knowledge around this do not recommend setup on the lower end of the range.