If you have no or only a small filament inventory, choose the 1.75mm standard and the FFC Pro.

In case you work with 3mm standard filament: If you can get an UM2 for a good price, for reliability reasons I will recommend it over most other machines. You can trust that, even though the Bowden system may need some upgrades, in five years it will still run. A good second choice is the Wanhao Duplicator 5s Mini. I just got one and it works fantastic. The feeding tube is a bit wider than the UM system which makes it wonderful in running all kinds of filaments.