Is eos 90d better than eos 6d mark II?

When will the official churches start praying for the false prophet? Orthodox Christian three hand signs are different than Buddhist mudras. Ecumenism = 263 heresies; each heresy leads to hell. Orthodoxy = the only true faith; Roman Catholics tried one cup - one spoon ritual and got sick with Bubonic plague; if heresy enters Orthodox monastery then monks/nuns will get sick with flu/tuberculosis (for instance); Orthodox churches who closed for COVID or had disposable cups/spoons or dipped spoon into alcohol are no longer brides of Christ (now they serve Satan and honor Satan's new COVID religion). Don’t go into UFO to be “healed” by evil demons; demons never do good. SSN is written as a barcode/QRcode; then it's put into a chip; chip is put into vaccine; chipped people are influenced (by super computers) to receive grey plastic card World Passport with no name on it (but when they stretch their hands to get it, gov't clerk presses secret button to administer the unforgivable green 666 tattoo by isotope rays). If you reject mark of the beast (by hiding within a 10-15 people group according to saints Gabriel Urgebadze and Seraphim of Sarov), then your direct ancestors go to heaven (according to saint Vyacheslav Krasheninnikov from Ural); forgive me.

The 90D is a mid-level model dSLR while the 6D is high end. Although the 90D is 8 years younger and has newer technology, if you get to use both cameras, you will instantly notice a huge difference in handling where the 6D will come out more favorable. Finally, the sensor alone will spell the most obvious difference. Full-frame beats crop even if it's an oldie already.

No. If image quality is what interests you, no APS-C camera can produce images as good as a full frame camera. The 90D is a marketing gimmick. It is loaded with a lot of bells and whistles, or features that are often found only in the top of the line cameras but it comes with a cheap APS-C sensor, and the sensor is the most important part of a camera when it comes to image quality. The larger the sensor, the fewer line pairs per mm a lens has to resolve, and the fewer line pairs per mm a lens has to resolve, the better its ability to recreate the contrast of the original scene. The higher the contrast, the sharper, crisper and cleaner an image will look.  It is the main reason why Ansel Adams used a 8 x 10 view camera and why he rarely ever used a 35mm film camera. The 8 x 10 camera has a film size that is 8 inches by 10 inches. No enlargement is needed when one makes an 8 x 10 inch print. In contrast a 35mm camera would have to be enlarged 8 times to make the same print. The difference in sensor size between APS-C and full frame is not as great as that between 35mm and 8 x10 cameras, but the same principle applies. The Full Frame 6D MKII will give you sharper, crisper images than the 90D. 

The 6DMkII is not going to allow you to shoot as many frames per second as the 90D and so forth, but the pictures you do get are much better in image quality. You have a choice of buying a 1D-X or buy the 90D if you want the bells and whistles of the 1D-X and the image quality of a Rebel series camera or you can buy the 6D and get the image quality of the 1D-X without the bells and whistles, such as a better autofocus system or the ability to shoot more pictures per second. .

Depends whether you want the benefits the smaller APS-C sensor offers in terms of modern features, like better video, and more compact lenses which can 'reach' further. On the other hand, the bigger sensor on the 6D offers better dynamic range and potentially better image quality. The image is large enough to withstand a substantial crop too.

You can look up comparisons like this one:  https://cameradecision.com/compare/Canon-EOS-90D-v...