Hi,
Slightly softer in the heel and front. I measured it , seems around 5mm more at heel and 3 mm at front. Significantly more impact protection especially at heel certaintly more stable. Weight is probably only extra 20-30 g, slightly bulkier at the heel. Buy it online on reebok and get it on sale ( I got it 50% off - blue and gold version - send back if not like it you have 30 days) or runningwarehouse. The EVA is only a heel cup around the foam to keep it stable -its full of the foam, so the quality foam throughout midsole.
Compared to forever energy, the HR3 has more impact protection (softer landing), more stable, more cushioned ride, and it has all the bounce and response of the forever energy but not quite as flexible. If anything I say because of the higher drop you seem to be pushed with faster transitions. The forever may be a faster shoe overall though but only been one short run in the harmony road 3.
The HR3 Upper is better quality too, good breathability . Cushioning levels are as high as new balance 1080 v9 and saucony triumph iso 5 levels, but the HR3 is more flexible, lighter , softer more responsive shoe. I am 75kg so probably needed more impact protection. You must try it.
Cheers
Steve