Thing about T-45 is that,
Anywhere I go, I will easily find the matts I need to repair the suit with very little searching, actually the only thing I need to find is a Power Armor Station. About half the time all the parts I need to make the repair are present on location without scrounging. That cant be said about higher tiers of armor.
As already addressed above most of the incoming damage will be as manageable by the "inferior suit." So essentially its a matter of do I feel like looking around for parts that I may not find easily?
For Power Armor unless you intend to face tank explosives....Which there is a mod for that! Barring face tanking mini-nukes your better off picking the suit based on how you feel with the way it looks