The Hardplate series by Rubicon Industries is a set of heavy-duty armor. No other armor series provides anywhere near its level of physical (not to mention overall) protection. Its thermal and chemical defense just about match the Ronson "R" Series and Shotlite Dragonfly armor, respectively.
Unfortunately, all this defense comes at the price of a high movement penalty for each piece, and the Helm and Gauntlets also increase reload time. Unless this set is used by a Heavy with a good amount of points invested in the Heavy Gear skill, augmenting the Pants and Boots with Machine Assisted, and/or putting points into Fast Movement, is practically mandatory due to the armor's hefty movement penalties. Augmenting the Gauntlets with Nimble and/or getting some points into Fast Reload will help alleviate the reload penalties of the Helm and Gauntlets.
It is not advised to equip the entire Hardplate series to achieve 99% resistance in each damage category: Though this series has the highest physical defense and excellent thermal defense, it's outclassed by Dragonfly and Medusa armor in chemical defense. Thus, players going for 99% resistance to all damage types should equip some pieces of Medusa armor, or, if enough points have been invested in BAE, simply go with full Graphene.
It better to equip them separately (mix with other armor parts). It is recommended to equip full set with well-defense Heavy if playing Apocalypse or Last Man Standing.