So both Klipper and Marlin+Octoprint use a Pi and an arduino (in simplified versions, the SBC and the MCU can be any boards but I’ll use those brand names to make it easy).

Marlin uses the Pi to display the web interface, then sends the gcode to the arduino. Then the arduino does the math to convert the gcode to motor commands. Gcode.

Klipper uses the pi to display the web interface, but it also takes the gcode and converts it to motor commands in the pi and only sends those simplified motor commands to the arduino.

So with Klipper the arduino doesn’t need to convert gcode which is a pretty intense computation. Also, gcode is actually pretty heavy to send vu serial over usb in Marlin and often the printer can print faster than the gcode can be sent. Which results in hang ups in the print, the printer pauses, especially in a print with a lot of curves and printing fast. Klipper can use the full power of the pi to make intricate motor commands, fine tuning acceleration and all to avoid vibrations (input shaper, it even uses an accelerometer sensor to refuse vibrations making cleaner prints and quieter printing)

Other benefits of Klipper, settings don’t need to be flashed to the arduino, they are saved in a text file on the pi. Changing Config is a simple text edit, then reboot to apply the changes. You can edit the settings right in the web interface.

One of the down sides of Klipper was that you had more functions in Octoprint with plugins, that’s not true anymore. You have many plugins compatible with Klipper with Timelapse exclude area, remote access, Obico (the spaghetti detective), and so on.

The web interface is much lighter and responsive than the bulky Octoprint. Octoprint was an afterthought while Mainsail was purpose designed for Klipper.

I used to run Marlin and Octo and hated the experience. Since I tried Klipper I can’t go back.

I was once at the exact same point where you are now. Marlin+octoprint really is good enough for most cases once you're up and running.

I pulled the trigger for klipper a couple of years ago and honestly never looked back. Mainsail is just so much more refined and usable than octoprint. Tuning Firmware Settings in klipper is so much simpler than marlin, it's just a breeze.

Combined with modern controller board (f.e. mks skipr), modern drivers like TMC2209, sensorless homing, Canbus-toolhead, resonance measuring, mmmh... chef's kiss ;)

Always be careful about the new thing. People tend to overhype the new thing and downplay the old thing. Klipper is neat! I've seen it do good stuff. However, Marlin is still good. Nothing wrong with it, either.

Klipper is great... Once you get it working. Way better than Marlin, but good luck getting it to work.

I swapped my motherboard for a BTT Manta + CB1 + EZ2209 drivers. Took about 7 months to get it to a state where my prints are regularly okay. Every 3D printing community I've come across is less than helpful, and all Klipper documentation is written like you're already at a pro level, as does pretty much every other guide out there. People will swear it's so easy, but you know what helped after 7 months of tinkering? Myself just throwing everything I have at my config in hopes of something working.

What kind of printer do you have?

gcode only contains high level instructions, e.g. "move 10mm on the X axis", which the firmware has to convert this to electrical pulses that can be sent to the stepper motors. If this is done naively the hardware wouldn't be able to follow the instructions due to inertia, filament viscosity, etc. Both firmwares have several methods to deal with this, but afaik Marlin does not have anything that does the same as Klipper's input shaper. Marlin has "linear advance" while Klipper has "pressure advance" which both try to solve the same problem but have different algorithms and you calibrate them differently. Using Klipper with calibrated input shaper will probably allow you to print faster than Marlin at an equivalent quality level.

Another difference is that all Klipper configuration goes into a text file, and you just restart Klipper to reload it. To change some settings i Marlin you have to re-compile the entire firmware and flash it.

Marlin's G29 command has different syntax depending on which ABL algorithm the firmware was compiled with, which IMO makes it more difficult to help other people who didn't compile their own firmware (i.e. who don't know which ABL algorithm their Marlin has).

They are both good!

I believe they both have pressure advance and resonance compensation. With klipper you get option for much better UI (Mainsail OS in my case) and you can change your config in a web browser.

The best part of klipper for me is being able to change pretty much any setting in a text file and restart and it works without having to screw around with SD cards, or firmware filenames, or compiling other than the first time.

For me the responsivity of Klipper UI was reason enough. Octoprint is unbelievably slow on the same hardware. The other thing was ease of configuration - no firmware compilation and flashing necessary. And the third is the actual printing performance - Octoprint has a really bad implementation of the actual print data transfer, and the serial interface routinely chokes on fine data such as arcs. That never happens with Klipper, even at much, much higher print speeds.

This might be situation dependant, but I personally (Ender 3 S1 Pro) spent weeks searching for ready-made firmware, then learning how to modify and compile firmware, then troubleshooting why I couldn't get Linear Advance working, only to finally figure out that it just plain wasn't supported by Marlin on my hardware.

I was about to give up and just go back to the stock Creality firmware, but decided to give Klipper a go without really knowing the full capabilities, other than that it natively supported Pressure Advance. In a fraction of the time I had spent dicking around trying to get a single feature enabled in Marlin, I had my printer running off a slick web interface, fully tuned up and printing substantially better than I was able to achieve with Marlin.

Now, granted, I never tried to get up and running with Octoprint so I probably am only half answering your question, but as a relatively casual printer I have found using and tweaking Klipper to be substantially more straightforward, and would not hesitate to recommend giving it a stab as long as you have a RPi laying around already.

There is post processing g code manipulation. Abl works this way, as does arc welder. If your bed is high on one spot there has to be some sort of manipulation after cura.