You don't want laser.
I mean, yes, you want laser. We all want laser. But, you literally are spending the price of four or five replacement lamps so you can get that feature, and should the laser fail, you are out all that extra money right away.
The biggest reason to go with laser is that they tend to offer some brighter projectors for business spaces and they are zero maintenance in business spaces where people don't have the brain capacity to replace lamps on their own.
But, in a home theater, it's rarely the ideal way to go, and your BenQ (what model?) is likely going to have better contrast than what you linked to because of the DLP chip which is in use. It is worth noting that with a 135" diagonal and a 17' viewing distance, you are not going to get any more image detail out of 4K than you currently get with 1080p. So, resolution won't improve the image. Colors available with native 4K content certainly would improve some.
But, the 4K DLP models would be a downgrade in contrast and you would increase the black floor for viewing.
Compared to the JVC 790 which will have a MUCH lower black floor than the BenQ you currently are using.
Most lamps these days are rated to 4,000+ hours. Then you have to consider how much you actually use the projector.
3 hours a day with a 4,000 hour lamp means about 4 YEARS of use before the first time you have to replace a lamp. If you keep the projector for 8 years that's only one new lamp.
Lamp replacement should rarely be the reason that someone goes laser unless they truly are watching 8+ hours a day.
Eventually, like in 8 years or so, we will be at a point where laser is about a $500 addition to the price and that most projectors are using it as their light engine. But, I would either wait, or go with a upgrade in image quality over light engine technology if I just had to upgrade right now.
I certainly wouldn't go with a business class laser projector. I might consider the LG or the Optoma UHZ65. But, would struggle because of the weak contrast on the new DLP chips. Especially if I had a good room and already worked with entry level DLP products (which I have).