MacBook Pro problems with sleeping

No. What you want is not possible.

When the screen is closed the behavior is the same to the user as if it went into sleep from another reason such as pressing the power button. There isn't any way to have closing screen sleep (called clamshell sleep) set to have a different effect than any other kind of sleep through user-accessible preferences. If you have your mac set to require a password after waking in the security preferences then the mac will ask in both cases upon waking.

However, the mac internally codes the reasons for sleep differently. So the computer can tell clamshell from idle sleep, and also can tell if the mac went to sleep for another reason such as power button press, low power or high temperature. Therefore it is possible that a third party hack can use these codes to enable different behavior. I could not find one, though.

When the mac wakes up there are similar codes generated by the OS so that it knows if the computer was woken by opening the clamshell, wiggling the mouse, pressing the power button, waking for network access and so on. This seems to create another opening for a third party solution.

A long uptime is four days? My MBP has uptimes of weeks. Not as snappy? I guess you're running out of memory or something else is wrong.

I've never had this issue where the machine is not as responsive after closing the lid as opposed to rebooting. I generally only reboot because of WiFi connection problems or software updates.

To answer your question - just close the lid. Only reboot when necessary. When closing the lid it goes into a sleep state which I think is very nice because when you open the lid it is almost instantly awake and ready to be used. While if you power it off it will take some moments to be booted.

You could leave the lid open as well if you like. The fist thing that is probably is gonna fail is the battery. To keep that in good condition make sure you keep your battery charged (there are other topics about this how to do this and what is the best).

In the end, the machine is built to be used and you should just enjoy using it without thinking to much about what is best. Apple already has that done for you :).