As soon as the project grows bigger and bigger, it's better to use higher level of programming to keep the project overview clear and all under control. Some bytes more or less doesn't care at all this days.

I started as an assembly programmer and I know how hard it was to keep an overview of a project with only 6 kBytes of compressed assembly code.

Then I started to use C when the projects were growing bigger. Now I'm programming a small ISDN PBX with one external S0 and one internal S0 with up to 8 ISDN telephones. The project has about 30 source files with the total source file size of about 1 MByte.

When programming the ISDN D-channel state machine I'm using a description languge to program in so called 'Protocol Description Language'.
This is highly compressed way of descripting a certain process with states, received messages, state actions and state transitions as a reaction to received process mesages.
PAS (Protocol Architecture Specification) file is compiled using Siemens PCT tools to multiple 'C' source files that are finaly compiled using embeded C251 compiler from Keil to executable code.

So if possible, stay away from the assembly language. With careful 'C' programming, you can keep your code size almost the same like using assembly language if you are using latest versions of C compilers.