I have had only good experiences with B&H in terms of returns, even when they did not make any mistake. I ordered a Sony a6000 from them, and only after several weeks did I notice banding on my photos. I had even thrown away the original packaging by that time, but they replaced the body. The new one also exhibited the same banding, and I found out (through the 'net and by trying a number of other a6000 bodies) that instead of being a manufacturing defect, that was Sony's dirty secret--the sensor bands and there is nothing you can do about it. B&H gave me a full refund, even though the product that they sent was not "defective" by Sony's standards. I can highly recommend them based on my personal experiences, and I have ordered tens of thousands of dollars of equipment from them over the years both for work and personally.

Depth of field is only effected by three things: focal length, aperture and distance.

In your example:

90mm focal length is the same
f/11 aperture is the same
distance to subject is the same

Therefore depth of field will be the same.

DoF actually does not change with sensor size/film format. (How we use different formats changes... going from full frame to APS-C or vice versa usually means either the focal length or the distance to subject or a bit of both must be changed in order to frame a subject the same way... and those do change DoF.)

And it certainly doesn't change depending upon manufacturer, brand or model either.

You might have trouble setting exactly 90mm on the zooms. Even if it's indicated on the zoom's focal length scale, often those aren't exact.

And a 90mm lens might actually be + or - 10% that focal length (at least, that was the tolerance the industry allowed in the past), so it might actually be anywhere from 81mm to 99mm, if accurately measured.

Plus, an internal focusing lens will actually change focal length when focused. I don't know about the Tamron 90mm (who actually sell a more expensive one that's IF and a less expensive 90mm that's not) specifically. But, for example, the Canon 100mm f2.8 USM macro lens is actually about 70mm when it's focused to it's minimum focus distance. You don't notice this change in the field... and it's more extreme with an IF macro lens due to it's extreme focusing range.

There's also can be some slight variation in aperture accuracy. However, that's usually very minimal. I recall a lab test for an non-variable "f/4" zoom I use that showed the aperture was actually something like f/3.9 at the wide end and f/4.1 at the more telephoto. That's probably true of most lenses, that their designated apertures vary slightly. But this is really "splitting hairs".

But, putting aside all those slight variables and assuming it were possible to keep all focal length, aperture and distance constant... there would be absolutely no difference in DoF.

You would see far greater difference from lens-to-lens in terms of resolution, sharpness, color fidelity and rendition, distortion such as "barrel" or "pincushion", chromatic aberration, coma, vignetting, and other image quality variables.

Wrong...The size and the shapes of bokah is directly related to the blade numbers and design...not really DOF created.

The out of focus DOF will take on the attributes of the aperture blades.

Some photographers are quite picky about the shape of the bokeh, and others could care less. Round and smooth is considered perfect by most.

High end lenses, like Canon and Nikon’s 24-70 f/2.8 both have 9 blades for example and do a great job.

Overall, the lenses that produce the best bokeh have 9 rounded blades and the worst have 5 straight blades.

Most lenses fall somewhere in between, with 7 rounded blades. For the most pleasing bokeh you will want to invest in a lens with more aperture blades.

If you’re looking to save some money, consider picking up a prime lens with at least 7 rounded blades.