For many the implicit simplicity of a hub gear is far preferred over the more exposed nature of a derailleur gear system, we'll leave it for you to decide which you think is better as it really is down to personal preference,but on a commute bike where often 'fit and forget' is the key, then hub gears can make sense.
The benefit is really gained from having all the working components of the gear system inside the hub body itself, sealed away from the elements and out of harms way. This is a particularly good idea if your journey may be along gritty gravel paths that will wear a derailleur and sprockets much faster, meaning extra expense when it is time for servicing. Note that the component that looks like a derailleur on this bike is actually just a chain tensioner to keep the chain taught during folding.
All the other components are the same between the I-4 and the D-9, so the difference between them is simply a choice of which form of gearing would best suit you.
If your preference is more towards a sporty performance feel, the Mezzo D9 with it's 9 speed derailleur may be more appealing, the actual range of gears you have on the two models are very similar, although the gears on the I-4 are slightly lower through the range, meaning that you have a slightly easier hill climbing gear on this bike, but at the sacrifice of top end speed.
The ease of fold, although not quite as intuitive as the Brompton is just as simple once you are familiar with it, and to be honest is just as quick. This, combined with the small compact folded size of the bike we would see this as a definite alternative to those who would only consider a Brompton as a commuter bike.
The new rear luggage bag available for the Mezzo has strengthened it's position as a serious commuter bike as well. The Mezzo bag is designed to quickly, simply and securely lock onto the Mezzo rack. The bag is very well made, with the appearance of a conventional smart cloth town/office bag fitted with carry handles and shoulder strap it really wouldn't look out of place in the office. Add to this the ability to fit in a laptop (it is well padded) and a lightweight yellow cover that can be fitted to keep the bag clean and keep you visible when on the bike in less amicable weather conditions.
We realise that not everyone that uses a folding bike is doing so to commute, but often the priorities are the same if you want to stow the bike in car, boat or camper for example (or just keep it in a cupboard).
The characteristics of a light weight bike, compact folded size and luggage carrying ability are universally appreciated no matter for what purpose the bike is intended, if we add to this the adjustability of the riding position, the quick yet confidence inspiring handling, and just the general positive feel that you get when you are on this bike you will appreciate that it will also be a fantastic bicycle for recreational use.
