Q: Why does it take so long to log in on the new update?

This is an area for discussing the Windows version of Apple Software Update. I've asked for your thread to be relocated.

tt2

How long have you waited after the update before giving up and reinstalling? After an update, the file system is reindexed for Spotlight (as least it has been for previous releases - I assume it is still the case) and for a few hours after an update (in my case - probably depends on your file system usage) everything is sluggish until that process finishes.

When you say login, do you mean

A) Your Mac was asleep and you wake it up, then enter your password to the screen saver?

B) Your Mac was already awake and you just enter your password to the screen saver?

C) Your Mac was awake, but you had use Apple menu -> Log Out, and now you are logging back into your account?

D) Your Mac was fully shutdown, and you are powering it up, and it is taking a long time to get to the login screen?

E) Your Mac was fully shutdown, you boot it, and that goes OK, but then when you enter your login information it takes a long time until you have a working desktop.

Just for fun, make sure System Preferences -> Startup Disk has your boot disk selected (you may  have to click on the padlock in the lower left corner to unlock it first).

You could try resetting the SMC and the PRAM

<Reset the System Management Controller (SMC) on your Mac - Apple Support>

<MacBook Air SMC and PRAM reset>

<How to Reset NVRAM on your Mac - Apple Support>

Finally, please post the output from EtreCheck

<https://discussions.apple.com/docs/DOC-6174>

<http://etrecheck.com>

detach all external devices on the mac from a shutdown state and reboot into safe mode

Try safe mode if your Mac doesn't finish starting up - Apple Support

if the boot process goes well reattach devices one at a time rebooting normally each time to determine if a device or combination of them is conflicting.

if that does not resolve the problem:

if you have file vault enabled it may cause a very noticeable delay between starting up and actually getting to your desktop.

Use FileVault to encrypt the startup disk on your Mac - Apple Support

in many cases 3rd party utilities that claim to "clean my, keep, snitch", etc are known problems and should be removed, additionally the findings on these forums show an overwhelming bad result with performance when a Macintosh Anti Virus solution is running. Mac AV is no where near the flexibility as Windows AV which has had ages to mature and has proven itself in many facets of security (currently no mac virus has been reported to exist in the wild, and malware variants are nowhere near the number of those that can affect windows users) - If you are adamant about using AV on the Mac try uninstalling to test, as it has been cited on these forums as having a distinct possibility of causing problems.

it's also possible you have 3rd party applications that are causing a delay between putting in your credentials and being able to use the computer.

if any of the methods described in the responses do not help try posting an etrechheck report for further analysis.

https://etrecheck.com

Try the things JimmyCMPIT and I have suggested, and also please post the output from EtreCheck we both asked for.

My wife has a 2010 Macbook Air and it runs fine with El Capitan.