I think you'd end up being unhappy with the LM3990. At 177 pounds you would have to anchor it to a solid, heavy stand or bench. But the real problem with it would be small X & Y travel distances. One of the things you mentioned in your first post was machining bolt hole patterns. The Y axis travel on this machine would severely limit limit you for that operation. There are ways around that but they are time consuming and less precise. I bought my G0759 not just because I never intend to turn it into a CNC machine but because I wanted the DRO. A DRO removes any backlash issues and has several other good features, most notably for me is a bolt pattern function. So easy to use. You can always buy any kind of mill but for what it sounds like you are going to use it for a DRO is highly preferable. And it's usually better to have it factory installed. Power is another issue with smaller mills like mine and I upgraded mine to a 2 1/2 HP treadmill motor. There are kits out there to do this too.
Once you start using a mill at home you'll get into a lot of projects that you are not anticipating right now. So my advice would be to buy a mill with the most travel, especially Y, and weight that you can afford to fit in your space. I know a massive Bridgeport, or clone, might be nice to have but they were built primarily for a production environment where reliability and machining speed were important. In a home hobby environment you don't need a machine that will run for 8, 16 or more hours a day for many years. And if it takes you 2 passes to make a cut instead of 1 on a Bridgeport, so what. You're using it for enjoyment, not work.