Anyone have any experience of the the 30Sxi or 30Hxi models?

They seem to have one of the greatest burner modulation ranges 28-5 kW
but I haven't seen any favourable or otherwise reports.

Or should I go with one of these two, which seem to be more popular on
this group:

Vaillant Ecomax 635 (new model with greater modulation than previous
models)
Worcester Bosch Greenstar 28HE system.

Quiet or noisy? For (upstairs cupboard other side of bedroom wall)

Any reason why the Glow Worm system model is cheaper than the
conventinal, even though it includes the pump and expansion vessel?

Any comments gratefully received.

TIA