I've had a bit of experience with electric bikes, as my university has biking stations loaded with them where we can "check out" a bike for a period of time, and return it later to be recharged and checked out by someone else.
They're fairly convenient, especially where I live - nothing but hills. However, they do become a hindrance as well. The electric motor makes it difficult to peddle on your own when you want, as the bike is so heavy that you lose motivation to. And then there's the hassle of securing it at your destination. A normal electric bike is fairly easy, you just take the battery with you. No one wants to steal a 50 lb bike, not worth the hassle. But if you have a pull-behind cargo/motor contraption like you linked to, it could be more difficult to secure.
I'm in the same boat as you, with about a 12 mile commute. When researching my options, I looked at various electric bikes as I can get one really cheap through my university. However, it's too cumbersome to really operate as a bike - too heavy to peddle unassisted on an incline, prohibited on most trails, too fast and cumbersome to react easily in traffic, too slow to keep up with traffic. After researching it a bit, I realized "Hey, these are basically overpriced, underpowered electric scooters". So, if you want to forgo the car but can't hack the bike, I suggest looking at various scooter options (not the kid scooter, the Vespa scooter). You can get an assemble-yourself no-name gas scooter that gets 60+ miles to the gallon for $500-$1000, or prebuilt brand name scooters for $1000-$2000. There's usually quite a few used ones on Craigslist as well, depending on where you live, as a lot of people get them for the novelty and hate them after realizing they don't have air conditioning, they aren't in a weatherproof box anymore, can't talk/text while driving, etc. If riding a scooter doesn't sound exciting to you, then neither will riding an electric bike. So go for the tough-it-out stance with the normal bike.