autofocus - Is the lack of AF Motor on the Nikon D5100 an important factor?

I had made up mind on purchasing a Nikon D5100 during the holidays but only yesterday I realized that it doesn't have a AF motor with it.

This is forcing me to change to Canon 550D which is in the same price range. I was more inclined to buy a Nikon so this is quite a change for me. The other cameras in the Nikon brand D90 and D7000 which have the AF Motor are not in my budget today. Also I notice that Canon 1100D which is less expensive yet has this motor in built into it. Why is Nikon giving this feature in expensive cameras only?

Apart from the fact that Af-S lenses are more expensive, is there any other drawback of buying a camera that doesn't have a AF Motor in it? As a beginner how does not having an AF motor affect the quality of pics?

Also, do mirrorless cameras have a built-in AF Motor ?

Answer

You have things reversed!

Nikon traditionally always put their motors in the bodies, offering supplementary lens mounted motors for additional performance on some high end tele lenses only.

To be able to compete with the very low end Canon bodies on price (which is the only thing most purchasers for that category consider when making a purchase) they decided a few years ago to introduce a few bodies without body mounted motors, and at the same time introduce a line of low end consumer grade lenses with lens mounted motors, primarily for use on those bodies (the D3000 and D5000 I believe were the first).

Canon has always (well, since the introduction of their EF lens mount back in (I believe) the late 1980s had all their motors in the lenses only, never in the body.

This of course increases the price of lenses, especially for people buying more than one lens, as now you have to buy a lens motor for every single lens (for that reason 3rd party lenses for Canon had often been slightly more expensive than the otherwise same lens for Nikon).

Both systems have their advantages. Having the motor in the body allows for simpler lenses, puts weight nearer the photographer, and reduces the system cost and weight for people having many lenses. Having the motors in the lens allows motors which are designed specifically for each lens, potentially allowing for lower power, cheaper, motors for smaller lenses (the motor in a Nikon D200 has to be able to power both a lightweight 50mm f/1.8 D and a very heavy 600mm f/2.8 D (which existed or was planned at the time, now the 600mm is only available as AF-S, with its own complementary motor).

The main thing you'll experience when buying a D5100 is that you won't have full choice of all F mount lenses, unless you are happy with manual focus on them. But probably, by the time that becomes a limitation, you'll be looking at buying a bigger body anyway, and no longer have that problem.