I'm suspicious about people who put too much importance into their language choice, maybe because I'm tempted to be one of them. You can love beautiful programs, or programs that get things done.
The former people tend to gravitate toward things like Haskell, which is very pure, conceptually beautiful, and feels like using the LHC to crack nuts. But hey, you're using LHC, great fun.
The latter will pick whatever ugly PHP framework is closest to the final product they want to ship. Most great startup ideas aren't very sophisticated algorithmically wise: existing mature libs in ugly languages beat writing/adapting everything in a cool one, although the latter is a lot more fun; an active and friendly online community, which is familiar with problems close to yours, beats having macros and first-class closures in your language; etc.
In theory people could love both beautiful things and getting things done, but in practice I find that the more strongly they feel about one side, the less they care about the other.
A corollary is that, in fun-to-use languages, everyone writes fun stuff rather than useful ones: frameworks, meta-programming stuff, continuation-based contraptions, etc. So you end up with a dozen half-baked neural network libs, but no decent (and _de facto_ standard) HTTPS client.
TL;DR: the overwhelming majority of startups are about social and economic hacking, not about software hacking. Over-focusing on the language issue is a clue that one hasn't come to terms with this sad truth.
Your characterization seems a bit too binary. When I have a choice I code in Python, because it seems to provide a really nice balance between beauty and practicality. It's an elegant, well-designed language that also has a rich, diverse, mature ecosystem of standard and third-party libraries and frameworks.
Agreed, Python hits a sweet spot, largely because GvR managed to maintain a strong anti-not-invent-here culture in the community.
Also agreed, I'm quite binary, if not caricatural, in my characterization. But it gets the point across, and I trust readers to put grains of salt wherever appropriate.
This being said, if like most projects, yours is more about reusing existing stuff than about writing software components that have never been released by anyone else before, and better-fitting components exist in PHP than in Python, You'll be better off writing ugly and not-fun PHP code. Some people can swallow this, others can't; the latters are probably better off not going the startup way.
I agree, Python is our language of choice as well. The logic we use is that it's in most/all of the cases the lesser of the two evils.
You can always argue "Oh! you are doing "that" use <said language> it's amazing and has that built in." However we find that Python focuses a lot on the programmer as well (white space etc...) and that was the tipping point.
While that is ultimately true, in the first days (especially pre-investment), the largest expense is programmer's salary, whether that is something you pay, or an opportunity you forego. Thus, getting to a fundable prototype twice as fast, or to a more robust system at the same time IS a factor.
Regardless of how much focus you put on it, it is usually the first "hard" decision everyone has to take in their tech-supported startup, and thus it gets a spotlight.
Agreed, salaries are the main expense; but not writing code goes faster than writing code in a productive language!
Unless you go to a completely unchartered territory (as e.g. Viaweb did), and there's no library to get you halfway done, you should pick the best library and just accept the language it happens to be written in.
Of course, a good language supported by a great community has better chances to have the best libraries. I'd even go further, and argue that "language goodness" should be defined by its ability to let great libraries and community emerge, rather than how fun and concise it is to code in it. This property is not entirely determined by the language's syntax, semantics, or even implementation, but it is what truly matters, what gets things done or not.
The former people tend to gravitate toward things like Haskell, which is very pure, conceptually beautiful, and feels like using the LHC to crack nuts. But hey, you're using LHC, great fun.
The latter will pick whatever ugly PHP framework is closest to the final product they want to ship. Most great startup ideas aren't very sophisticated algorithmically wise: existing mature libs in ugly languages beat writing/adapting everything in a cool one, although the latter is a lot more fun; an active and friendly online community, which is familiar with problems close to yours, beats having macros and first-class closures in your language; etc.
In theory people could love both beautiful things and getting things done, but in practice I find that the more strongly they feel about one side, the less they care about the other.
A corollary is that, in fun-to-use languages, everyone writes fun stuff rather than useful ones: frameworks, meta-programming stuff, continuation-based contraptions, etc. So you end up with a dozen half-baked neural network libs, but no decent (and _de facto_ standard) HTTPS client.
TL;DR: the overwhelming majority of startups are about social and economic hacking, not about software hacking. Over-focusing on the language issue is a clue that one hasn't come to terms with this sad truth.