Inches or metric?
This is one of the most important decisions you will make in buying equipment for beginning machining. It's at least as important as brand of machines you buy, the size of these machines, or their cost. Once you select a unit to work in, you will quickly become accustomed to it and begin to think in terms of it. It's easy to buy and use a new machine in your accustomed units- but attempting to change units is a very difficult and frustrating endeavor.
Decimal inches offers a nice advantage, in that it just happens to be a very practical set of units when applied to machining:
1.0" is a useful unit for describing a length of material to be machined.
0.1" is an easy unit to rough cut material to (such as with a bandsaw).
0.01" is an easy unit to do quick 'rough' machining to.
0.001" is a very good practical limit to the accuracy realistically attainable by a good operator with good machine tools.
0.0001" is a good practical limit to the accuracy realistically attainable by a good operator with good grinding tools.
On the other hand, the metric system enjoys worldwide acceptance and use. If you're not in the US (or perhaps Canada), it may be entirely impractical to use a machine that requires fractional inch sized components when you simply cannot easily get those parts.
Of course it's entirely possible to create metric sized parts on a machine with 'standard' units (and vice versa)- but you will need to decide what units will be best for you to work in.