I know all these languages but Basic, and I strongly recommend Python for bots. Python is (1) dynamic, (2) has lots of libraries related to http, (3) programs writen in python are readable and short, (4) supports OOP, functional, declarative, procedural styles, (5) the programs will work on almost every OS you can imagine.
There are a few flaws in it tho. It's the slowest of the lot, it doesn't work with threads well (but as you're going to write bots, your threads will be in IO waiting state most of the time, so you won't see the difference).
>C#
Requires to write a lot of boilerplate code. Its' static typing is good for corporate development, but for bots I'd choose something other. You might choose c# tho if you need bots with GUI.
Also pure OOP is overrated shit. C# 3.5 goes in the right way with LINQ and expressions, but still it is not enough flexible for personal use. IMHO.
>VB (classic)
Legacy language, Delphi is better in every perspective but the price.
>4. Perl
Python can do everything Perl does, but easier. Perl language often produces "write-only" apps. The advantage of perl (and even more of php) is that it is supported by default on almost any hosting, even free one. Lots of scripts already done in perl, so you will have lots of working examples. It's usually slightly faster than python.
>Delphi
Inferior to C#. You might use Delphi if you need unmanaged GUI app, which does not require .Net framework, as it is usually easier to do this in Delphi than in C++. It will probably produce the fastest code of the lot, but if you're really after speed, I'd recommend C++ or pure C.