Advocates of class-based object models who criticize prototype-based systems often have concerns that could be seen as similar to those concerns that proponents of static type systems for programming languages have of dynamic type systems (see Datatype). Usually, such concerns involve: correctness, safety, predictability, and efficiency.

On the first three points, classes are often seen as analogous to types (in most statically typed object-oriented languages they serve that role) and are proposed to provide contractual guarantees to their instances, and to users of their instances, that they will behave in some given fashion.

On the last point, efficiency, the declaration of classes simplifies many compiler optimizations that allow developing efficient method and instance variable lookup. For the Self language, much development time was spent on developing compiling and interpreting techniques to improve the performance of prototype-based systems versus class-based systems. For example, the Lisaac compiler produces code almost as fast as C. Tests have been run with a MPEG-2 codec written in Lisaac, copied from a C version. These tests show the Lisaac version is 1.9% slower than the C version with 37% fewer lines of code.

Finally, the most common criticism made against prototype-based languages is that the community of software developers is not familiar with them, despite the popularity and market permeation of JavaScript (notably, current work on a fourth edition of the ECMAScript standard seeks to turn JavaScript into a class-based language). Further, as prototype-based systems are relatively novel, and few and far between, best practices for software development using them have not become widespread.

Advocates of class-based object models who criticize prototype-based systems often have concerns that could be seen as similar to those concerns that proponents of static type systems for programming languages have of dynamic type systems (see Datatype). Usually, such concerns involve: correctness, safety, predictability, and efficiency.

On the first three points, classes are often seen as analogous to types (in most statically typed object-oriented languages they serve that role) and are proposed to provide contractual guarantees to their instances, and to users of their instances, that they will behave in some given fashion.

On the last point, efficiency, the declaration of classes simplifies many compiler optimizations that allow developing efficient method and instance variable lookup. For the Self language, much development time was spent on developing compiling and interpreting techniques to improve the performance of prototype-based systems versus class-based systems. For example, the Lisaac compiler produces code almost as fast as C. Tests have been run with a MPEG-2 codec written in Lisaac, copied from a C version. These tests show the Lisaac version is 1.9% slower than the C version with 37% fewer lines of code.

Finally, the most common criticism made against prototype-based languages is that the community of software developers is not familiar with them, despite the popularity and market permeation of JavaScript (notably, current work on a fourth edition of the ECMAScript standard seeks to turn JavaScript into a class-based language). Further, as prototype-based systems are relatively novel, and few and far between, best practices for software development using them have not become widespread.