My advice would be to choose a system that matches the requirements and not preclude either solution. Combis have their attractions, as do storage systems, but there is no one size fits all solution. I have had both setups in this house, and both have pros and cons. Yes either system can be "perfect" in an ideal world, but it is very difficult to achieve perfection in the real world with real budgets. Exotic solutions exist for combis and storages systems (and systems that are a mixture of both). It seems rather too easy for the proponents of one particular technology to talk about the exotica as if it is routinely fitted mainstream stuff. For most users the generalisations (flow rate, space, performance etc) are mostly true, even though there are exceptions to the "rules".