Beware that the Y travel on the Syil 5 series is as short as that of a Tormach 440.

Which tool is right for you depends entirely on what materials you will be working in (plastic, aluminum, steel, titanium, ... ?) and how big the parts are going to be and how patient you will be when you make them. (Also: for any material/cutting operation that needs flood cooling, you want an enclosed cabinet.) The precision, finish, and ability to cut harder/tougher materials depend a lot on the spindle power and the rigidity/weight of the machine. Depending on what you want to do, a used Bridgeport manual might be the right choice -- we know way too little about your project to tell for sure.

Other options include desktop 3D printing (for plastic parts) and sending out for 3D printing (high quality plastics, and materials) to places like Shapeways, or sending out parts for manufacturing/machining to contract houses or people on this forum. You don't HAVE to have a mill to do prototyping yourself. The cost of a mill will pay for a lot of plastic parts from Shapeways!