Center motor ebike costs more, is it worth it?
Yes, in general mid-drive bicycles are better than hub drive. There are technical reasons and economic reasons.

Technically, mid-drive can be more efficient as they can take advantage of the rear derailleur or internal-gear hub to work at optimal speed. Hub-drive motors can only be optimized for one-speed (although some 2-speed hub drives have emerged). 

Furthermore, the pedelec sensors on mid-drive can be more sophisticated in measuring torque rather than just rotational speed. This is because their location on the bottom bracket makes torque measurement easier. Hub-drives usually rely on just a magnetic crank speed sensor. However, note that not all mid-drives measure torque - and some better hub-drives do swap out the bottombracket and put in torque sensors.

In terms of weight and balance, the mid-drive is better located. You want your weight to be low and in the middle. However, geared hub-drives are also getting lighter and smaller. Furthermore, the battery is often the heaviest component and so battery placement itself is critical. The best units have the battery behind the seat-stem or in the lower part of the main triangle. 



Finally, there are non-technical reasons why mid-drive is better. There are only a few mid-drive manufacturers that are extant: Bosch and Bafang (I'm leaving out Panasonic, Yamaha, and Shimano mid-drives as they aren't commonly available outside Japan). This means if you get a mid-drive, you're getting it from a well-known company that has a strong reputation (Bosch much more so than Bafang). Your mid-drive bike above looks like a Bosch but it has its markings removed and the store website doesn't have any details -- so you might want to ask and avoid it if it isn't Bosch or Bafang.

Hub-drive motors on the other hand are made by a wide variety of companies. So unless you know the company's reputation, you are taking a risk. You're much more likely to get a no-name hub motor with a no-name controller. 

Finally, note that the Bosch, Panasonic, Yamaha, and Shimano mid-drive systems all require specially designed bicycle frames (bottom brackets). This means that the bicycles are much more expensive. Bafang mid-drive and all hub-drives can be bolted onto any OEM bike frame so they are much less expensive.