Can't find the page on the Synapse alloy but looked at the specs on the rest and they all run similar. Few downgrades on some manufacturers on Cranksets and a few detail changes but they all have the same problem as far as I am concerned. That is the wheels. I DO NOT LIKE INHOUSE WHEELS. It is the main point where to get to a price- the quality will be cut. It drives me nuts that they come up with a good bike with good components and a sensible price and then downgrade the bike with the one thing that will be noticed whilst riding the bike. That is other than fit and comfort of course. The one exception is the Bianchi and I do not know these wheels. They have a funny spoke pattern so I would like to find reports on those before committing to quality
Easy way out of this and that is to get the shop to change the wheels before purchase- making an allowance for the unused OM wheels of course.
Although I am a giant man- I don't think that any of these bikes will differ greatly. The choice is going to be down to the test ride, The shop and staff and the size of the wallet.
But remember- A Bianchi in celest colour is worth 5mph on your top speed.
I still have a Bianchi but you will not want to know about that as it is an 11 year old MTB that has been abused for all its life--And it is celest in colour.