Very similar to " what van is the best" or "what car is the best". Both examples, have and will be causing disagreement for ever and a day.
OP asking "what boiler to buy" have no idea who's, who, and unfortunately there are far to many pretend experts who have the gift of writing convincing garbage.
...
People are still been bombarded with carp advice dished out by unqualified fools, but when installers bring this to light they are accused of bickering
I will not be stating my opinion on which boiler is best.
I have absolutely no problem with engineers / installers discussing the merits or otherwise of different boilers until the end of time. However when it becomes a match to see who can come up with the nastiest names to call each other this isn't helping the OP make their decision.
Of course if the thread doesn't involve an ordinary householder who's just made their first post to the forum, then claws out and fight to the death if you like!