I had a mill drill years ago. Now,I have a BP clone of good quality,42" table. The BP type mill has a head that can be tilted both ways(sideways and "nod"). Your present mill will not nod. You can make up for that with tilting vise,etc.
The BP will accommodate much heavier parts on the table. I believe the load limit is about 750#. The work envelope is much larger.
The BP is much more rigid than your present mill. The head can be accurately trammed in,something I never got true on my mill drill(mine was a round column. As the head went up and down,the column would bend enough to change the tramming.
I don't think the price is out of line with the APPARENT condition of the mill,though a picture cannot tell the whole story,obviously. You will not have trouble getting parts for the BP,but you certainly WILL have trouble ever getting parts for an import more than a FEW years old. Import machine motors do not have their motor's armatures dipped in insulating varnish,and they CAN suddenly short out. I had that happen on one. Shorted across the motor bearings. Had to be replaced. But YOUR motor is a special type that cannot be replaced with a standard motor I THINK. I haven't taken your type mill apart. But,if the shaft incorporates gears,etc.,a normal "C" face motor will not fit. Never put a lot of faith in Asian electrical parts.
So,you have the issue of a larger work envelope,reliability, rigidity,and parts availability. See if you can rent a trailer like the one shown. Turn the BP's head upside down,and CAREFULLY lash it down while driving. I used to worry about moving a 10" x 24" bench lathe. Now,I have moved 8000# lathes,BP type mills. You just have to know how. I keep a pair of "Johnson bars",otherwise known as lever dollies,or pry lever dollies. Northern sells all steel versions cheap. Mine have long oak handles. With the longest oak handles,you can get the "shovel" end of the lever dollies under a machine and lift 5000#. 2 men can slide a BP around pretty easily on a CLEAN concrete floor. Just lift the mill enough to SLIDE the machine,not tip it over!!!!!NO little crud on the floor to jam the dollie's wheels. I also have used a comealong to pull machines into place. But,you need a steel pole,or some way to securely anchor the end of the cable to. We turned an 8000# lathe end for end and pulled it 20' using a comealong,a clean concrete floor,and 1/2" steel bars under the lathe's pedestals. They had to be re inserted when one popped out from under a pedestal as the lathe moved along. It was fun.