I will repeat what others have said, if at all possible go to a big show and try as many of the machines as you possibly can, sit down, stand up etc. If there are any classes local to you for any brand go take them. One of my LQS had an HQ educator come in and most the people attending do not yet own either a sit down or stand up machine.
Check if there is a shop near you that rents time on their machine. There is one 15 minutes from my home and one an hour from my home. Different machines, but will give you an idea of how they feel. Plus you get to complete a project.
Find out which dealers service your area. The machine heads are very heavy, will the dealer come to you? Will the dealer set up for you? Does the dealer offer any lessons?
Due to the expense of these machines it is worth your while to spend the time and money fully investigating your options, it will not be time wasted. I was looking at traveling away for a weekend to rent time on a machine that was different from the ones available locally. Then I realized that I would feel more comfortable with a local dealer, so that narrowed my options.
Think about your current and long range living situation. If you buy a LA on a frame, will you have room for it if you move in 5 years? Many have to sell due to downsizing.
Consider buying used. I did from a woman in the situation above. She could not fit her LQ in her new home. She sold it to me and was going to buy a HQ Simply 16 on the Little Foot Frame. I plan to live in my home for the next 30 years, so I know I have room for my machine for the long haul.
In a few years I may upgrade. Where I live there is a demand to used machines, so I am not worried about finding a buyer for the one I have.
Oh I do not like basting, so for me a sit down machine was not an option.