All computer systems need some kind of monitoring to ensure they work smoothly. While Mac OS X has a pretty decent pre-installed system monitor, there are other options that one can choose from. Some of the best of these have been mentioned below.

MenuMeters

This free software is perhaps one of the best system monitors that can show all the statistics in one place: the menu bar. This makes it unobtrusive and doesn’t hinder your everyday work on your Mac. While it does give you an idea in one glance, you can even go into the details of what your system is up to. Moreover, the statistic can also be displayed in percentages while the way you want memory usage to be displayed is also an option. Although the software is a pretty wholesome option, there are areas where it lags behind. These include its insufficiency to provide a detailed graph of performance and the lack of a history record. Moreover, it might hog your menu space too.

iStat Menus

This software will cost a few bucks ($16 to be exact) but provides with a detailed review of the system including RAM, memory usage, temperature, network activity, fan speed, etc. The best thing about this particular system monitor is that it enables the Mac user to keep a check on the hardware as well. It will let you know if it is time to buy a new battery or an upgrade altogether. Moreover, it also provides with previous data as well so you can monitor your Macbook more closely. The only major drawback that it comes with is a bug because of which the memory usage tool might act up.

Disk Doctor

If keeping a check on the available storage or wanting to get more storage is what you’re looking for, then Disk Doctor is your solution. Costing a meager $2.99, this utility will help create space in your system by deleting old, unused data. On the downside, Disk Doctor isn’t a multi-purpose software and will only take care of the memory bit.

MagicanPaster

Magican Paster is closer to iStat Menus than any other software available. It also monitors disk, RAM, CPU, battery and the network of your Mac and that also in individual windows. Magican adds fun by presenting data in a colorful way. What is even better is that this utility is free of cost. It does come with its share of drawbacks. It is only a monitoring device and will not aid in maintaining your Mac. Moreover, multiple windows can be a hassle.

DriveDX

This is another software that keeps an eye on the SSD as well as the HDD. It informs on whether a certain system requires repair or replacement and helps perform diagnostics. It also keeps a S.M.A.R.T. error log along with a drive temperature alert. It costs $19.99 with other license versions costing more according to the number of users. It backs up current data and helps in retrieving old data as well.
Overall which system monitor is best for you depends on exactly what you are looking for. If you want an all-rounder, iStats is perhaps the best option for you because it is cheap and will so the work.