How much harder would the Haute Route be? Would you consider doing the Tour du Mont Blanc instead as a less difficult option?
Well, having done both I can safely say that the haute route was harder for me. I've finished the Annapurna in a relatively good condition last year, and finished the haute route with 2 kneepads, a sore ankle and had to buy better trekking poles thru-out the trek (haven't used a trekking pole at all last year).
However, my friend Ophir who has done both treks with me had the exact opposite experience! He had a hard time breathing in the Annapurna heights, while this trek was a breeze for him and at one point he even started running downhill!
I guess it all depends on how well do you manage downhill trekking, as in the haute route you'll have to tackle 1.5 km and 1.6 km height loss at certain days, which is very rough for some people (me).
Tip: carry only what you need! I was packing about 14kg, which turned out unnecessary. You can certainly go as low as 9kg without compromising a lot on your personal hygiene :)