I like my M+ for general and commuting use, about 4k miles between two sets of 700x35 and not had a puncture yet. There is a weight penalty which I can feel when accelerating or going uphill. But I don't find they roll as bad as some online postings might suggest. When I was commuting regularly last year I did some comparative rides:-
The Giant you're familiar with - 23mm tyres, no rack etc and total bike weight of about 21lbs I could manage about 18.5mph over 20 miles
Using the Surly for the commute and taking the average speed for the round 40 mile trip, to try to balance out wind direction etc - I could manage 15 to 15.5mph - the bike has guards, rack, hub gear, 700x35 M+ tyres and weighs in at about 33lbs, plus I had a pannier on for the commute.
How much of the speed difference is attributable to each part is impossible for me to calculate but it's not just the tyres.
It's got to be down to how much you want to spend and how much you value weight versus punture resistance. You can get 700x32 tyres down as low as about 330g and this rises through the options to 800g for the M+. The route matters as well, how many/severe the hills and expected surface conditions you'll be riding over.