A given blower's performance is a function of the pressure difference between its input and output. The specified blower performance is that of the blower hanging in free air (zero pressure loss). Hence, it doesn't matter (all other things being equal) whether the blower is in the hood pushing into the duct while pulling from the partially sealed house, or placed on the roof pulling from the duct and also from the partially sealed house. In specific cases, for example Wolf hoods and blowers, the internal blower may be different than the same-rated external blower, so fan curves for both should be examined in the context of the pressure losses that will be present. With decent MUA the dominant pressure loss should be the baffles.

The achieved volumetric flow rate of the hood and blower determines whether the rising and expanded cooking plumes are contained by the hood; that is, pulled past the baffles. It is the hood overlap of the plumes that determines capture of the plumes. Both functions are needed. A shorter front-to-back hood may miss some cooking effluent and that effluent will distribute itself about the kitchen and house.

If an internal blower has the same performance at the expected pressure loss as an external blower, then convenience of access vs. reduction in noise becomes the major trade-off. Most like less noise as a priority, particularly when the number of times one is subjected to noise is vastly greater than those where one needs easy access to a roof blower. Note that reduction of noise is only modest with a remote blower unless a silencer is included in the duct path.

A 42-inch hood with 27-inch depth (of which probably only 24 inches is entry aperture, provides roughly 2 x 3.5 = 7 square feet of aperture. For this the blower needs to move about 630 CFM for the hottest likely residential cooking. This means that the blower has to accomplish this at some pressure loss. A 1200 CFM rated blower will likely achieve this so long as the MUA pressure losses are slight. (This is another whole bag of worms.) In any case, one shouldn't dive into hood and blower purchases without also resolving how the MUA will be supplied.

There are both safety considerations and complexity considerations when choosing an MUA approach.

Wow, super helpful response! And thank you for helping me distinguish between (and understanding the dual importance) of capture and containment. I’ll be stopping by the appliance store again tomorrow to further discuss hoods so I’ll bring up the topic of MUA. I guess I’ll be spending this evening scouring this forum for prior MUA discussions. Thanks again!

P.S. For anyone in the future following this thread, I recently discovered that the baffle placement/angles of the 24" depth vs the 27" depth on the Wolf pro hood is different. For example, on the 24" depth, the baffles are over the rear burners and are angled towards you. The baffles on the 27" depth are angled towards the backsplash wall and there is either stainless steel panel or cutouts for heatlamps at the rear instead. Aside from the obvious benefit of the deeper hood, I also feel like the baffle angles may be better too? Perhaps that's just an incorrect assumption on my part. But now I'm leaning towards the 27". :)

Baffle angles above horizontal provide at least two advantages. The primary one is to move captured grease down to wherever it is being collected. This is mostly important for commercial hoods, and as I recall, they have to have an angle of at least 45 degrees above horizontal. Residential hood grease collection may be so modest that grease movement need not be particularly aggressive; the grease will harden on the baffles to be removed when cleaned.

The secondary advantage of baffle tilt is to increase the capture volume below them. This is mostly important to residential hoods, because commercial hoods already have a large volume between the entrance aperture and the baffles. Residential hoods typically try to make baffle removal convenient so one end is near the entry aperture.

It is OK to have internal sheet metal angled such that it progressively restricts the sectional area between entry aperture and baffles so long as the volumetric flow rate at the aperture is high enough, and the internal slope angles favor upward plume reflections. Ultimately, the air velocity at the baffles has to be high enough to entrain the parts of the plume which otherwise would reflect from the baffles and try to escape the hood.