When comparing PuTTY vs iTerm2, the Slant community recommends iTerm2 for most people. In the question“What is the best terminal emulator? ” iTerm2 is ranked 2nd while PuTTY is ranked 7th. The most important reason people chose iTerm2 is:
Other than being able to customize the various shortcuts, iTerm2 also lets you customize the colorscheme, font, transparency, etc.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free
Pro De facto standard client for SSH, Telnet and Rlogin on Windows
PuTTY is one of the oldest and most popular clients. It has earned the trust of a great number of users over a long period by being reliable, offering useful features and helpful support. It got into the 15 Essential Open Source Tools for Windows Admins list by InfoWorld.
Pro Can be used on any Windows computer, even without admin rights
Pro Source code available
Full source available. Compile and modify it yourself.
Pro Lightweight and portable
Doesn't require much resources (memory and hard-disk). Can even be run on a system by just downloading without install.
Pro Extremely customizable
Other than being able to customize the various shortcuts, iTerm2 also lets you customize the colorscheme, font, transparency, etc.
Pro Autocomplete is built-in
iTerm has autocomplete features built in. It remembers your past commands and when you are writing something on the terminal, simply pressing Control-;
it will show you a drop down menu of suggestions from which to choose.
Pro Complete out of the box
Unlike most terminal emulators, iTerm2 comes with a pretty complete set of features. It has built-in search, autocompletion, tabbed navigation, Growl support and even a built-in clipboard manager for various API keys and such.
Pro Fine tuning for fonts
It's possible to choose a font and adjust vertical and horizontal spacing.
Pro Can immediately open files inside a text editor
You can Ctrl+Click on a file path to open said file in a text editor.
Pro Supports mouse actions
Has support for mouse actions like clicking, dragging, selecting, etc.
Pro Active maintainers
Issues resolved fast by quality contributors.

Pro Works well with powerline fonts
Pro Completely free and open source
iTerm2 is completely free and open source. It's released under the GPLv2 license.
Pro Split panes
Easy to split panes to either horizontal or vertical sections. Makes it easy to observe multiple console windows.
Pro Supported by many applications as a terminal app selection
If an application has terminal integration, there is high probability it allows iTerm2 to be selected.
Pro Intuitive
Pro Cmd+Shift+I to Input all
Wanna SSH your server from multiple tabs, here you go.
Pro You only need to type in commands once
iTerm2 can store up to 4M of history of commands you already used. This, coupled with the built-in search features makes it possible to type a command only once and then search for it through the history for subsequent uses.
Pro Works perfect with Oh My Zsh
It's a perfect base to add Oh My Zsh on top of it and enjoy a lot of themes and a really pleasant look and feel.
Pro Works well with tmux
The great mouse and clipboard support that are built-in go really well with tmux.
Pro Any key can be mapped to any function
Using the Preferences Menu you can set up hotkeys to map virtually any action you can think of to a single key or a combination of them. This is extremely helpful as it allows you to use shortcuts to edit commands you are typing in the terminal and while most terminal emulators have shortcuts for this sort of thing, few of them let you define your own.
Pro GPU-rendered, blazing fast and super smooth
Many people say they use Kitty or Alacritty because they are GPU-rendered. That was true a long time ago. But iTerm2 has been GPU rendered for years now. It's so fast and smooth that you soon forget you are in a terminal.
Pro Beautiful, minimalistic and elegant UI
It's super-clean and during use it gets completely out of the way, it's a beautiful canvas for your terminal work, a pure joy that never gets old.
Pro Can be configured as a drop-down terminal
Can be configured to work as a drop down terminal like Quake.
Pro Cmd+D to split plane vertically
Very handy to use multi-tab.
Cons
Con Only one session per window
Cannot open a second session in the same window (you need multiple windows).
Con Can not save passwords
Anyway, you can use "PuTTYgen" to generate a key pair, then use "Pageant" to do a password-less SSH remote login.
Con Lacks features
It is JUST an SSH client. There are many other options with built in X-servers, Multitabbing, etc.
Con Ugly design, too simple
Looks very dated. Does the basic functions very well, but not much more.
Con No global settings
If you want to change a setting for all your connections, you'd have to do it individually.
Con Organizing sessions
Does not have features for organizing session connections (like folders). If you have 5-10 connections that's fine. But if there are 30-50 connections - that becomes a nightmare.
Con Tedious logging/tracing
Its tedious to set up logging and tracing (e.g. for serial connections).
Con No login scripting
Con Keycodes are not passed through following Linux standards
If you come from a Linux terminal emulator (Gnome Terminal, Konsole...) and you rely on key-combos that are widely supported in those, porting the same functionality to iTerm is possible but will require a lot of research and configuration on your part, so account for a long painful adoption period.
Con Not quite as fast as Alacritty or Kitty
Comparing these 3 terminals on the same machine/config, iTerm stands out as the slowest of the bunch. The difference may not be noticeable to all users.
Con Way too many menu items and settings
Finding the right one is like searching for a needle in a haystack.
Con Doesn't support Snow Leopard 10.6.8
Some people still use Snow Leopard or other 32-bit systems.
Con Doesn't support RTL
