PETG is a middle ground between PLA and ABS. It has the ease of use of PLA while being as strong as ABS. With that said, PETG demonstrates better strength than either PLA or ABS, even though for many years ABS has been the common choice for printing stronger items.

PETG vs ABS vs PLA
How do these materials stack up especially with regard to their strength and suitability for outdoor use?
For most applications, PETG comes out strongest. It is more durable than either PLA or ABS and offers a more weather-resistant option. ABS does have a higher glass transition so it can be an option for applications with high temperatures.
In terms of which is easiest to print with, PLA is the obvious choice. The high printing temperature of PETG limits the number of printers that can work with it. PETG is also more unforgiving, becoming brittle if the wrong slicer settings are used. It is this extra sensitivity to print conditions which make PETG more difficult to print with.
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ABS has a problem with adhesion. It tends to warp so requires a heated print bed to make sure it sticks. Warping is not as much of an issue with PETG. The adhesiveness of PETG is almost too good as prints sometimes break when removed from the print bed.
What Is Stronger Than PETG?
PETG excels over stronger materials because it is easier to print. Printing with stronger materials like nylon, polycarbonate or composite filaments requires printers that have improved capability. These types of printers are typically much more expensive.
Professional grade filaments cost more and they are used on more expensive printers. They are also harder to print with. There are several types of harder filaments and composites which offer better strength than PETG.
Nylon
In World War 2, all nylon was commandeered by warring countries to make parachute cords. Today, nylon is one of the most commonly used plastics and is found in everything from dental floss to seat belts. Whether through injection molding or 3D printing, nylon produces items that are chemical, weather and impact resistant.
Polycarbonate
Polycarbonate (PC) can be used to produce transparent items. Its strength and transparent qualities are why it used to make anti-riot shields, helmet visors and bulletproof glass.
Carbon Fiber
PLA, ABS or nylon can be reinforced with carbon fiber to produce a material that is stronger but also lightweight. This makes it ideal for printing moving parts that experience compression.
Metal
Metal is a fairly recent material. It has greatly expanded the scope of what you can 3D print because it is stronger than plastic filament. Metal filament is made through mixing a high concentration of metal with plastic.