How to choose between British and American English for technical documents

The differences between British English and American English are more apparent in speech than in writing, where the main indicator of variance is spelling. You have to consider who your readers are, and adapt your writing to their expectations. Do you have any particular example that is bothering you?

I think you're possibly worrying unduly about this. Both the UK and US have active electronics industries and research programmes and UK speakers are used to reading documents written by US speakers and vice versa. I aslo wonder how much difference there really will be for your purposes anyway, beyond a few minor spelling differences.

So I would just choose the variant that's most practical for you: are you more used to reading literature from US or UK researchers/manufacturers? Can your more easily get a US or UK proofreader?

The International Organization for Standardization favours British spellings, spelling the -ise/-ize suffix with a z (which is valid, though rare, in British usage, and standard in American usage).

The International Union of Pure and Applied Chemistry has settled on the British spelling (and pronunciation) of aluminium (not the American aluminum), but the American spelling of sulfur (not the British sulphur).

That might give you some guidance. (This system is known as Oxford spelling.)

Based on your question, it seems that you are free to choose so, you can choose which English to use based on your, personal preference.

Is there any reason because I should use one over the other?

The main reason for choosing one form of English, whatever the context, is your audience. Who you will be communicating with, in the language.

You mentioned that it will most likely be European people, so , you can use British. As far as I know, American English is not the language of any European country (not even the UK) so it is not necessary to limit yourself to it. It is one, particular dialect that is very different from others. There is no particular need to use it, unless you know beforehand, that you will be communicating mainly or only with, people who speak American English.

Generally, there is no problem speaking or writing in, the English form of English. I have not had any problems communicating with other people from the English-speaking world (apart from Americans) and the non, English-speaking world, when speaking and writing in, English English. I have visited a lot of continental Europe and met many continentals who spoke English. Generally, I had no problems in being understood by them. The only exception being two, different people, who were learning American English, in particular.