Those are some funny looking portable easles.
I would take a look at the first one. Looks like an old beaver saw (very well built). If possible you want a belt driven saw like the first. Generally the motors are more powerful and will do better with ripping or lage pieces of hardwood. The belt will also protect the motor from burnout in heavy use.
The arbour on some contractors saws can be quite out of square or have significant runout.
The contractors saw will do fine for light duty and occasional use though.