I know that there are many kinds of alternative coins existing today, but is it better to have that many coins instead of having just a few? What are the benefits and harm in having that many alternative coins?
It all depends on the intention nor the abilities of each, especially in terms of management.
There are many different digital currencies each has distinct advantages and disadvantages. Some offer a lot of innovation, supply, a team of reliable developers and different potential. Meanwhile others are offering little innovation but have great features. Of course this can make your choice quite complicated. The same thing by having a lot of coin.
However by having many coin of course the chances of success are numerous, as said, by
Chuokie.
Keeping too many coins has more chances that you can earn a fortune from one of them, though, same with the bad side that some coins are just waste of money but at least if you have more profit than losses then it is fine. Holding a few coins will just hold you back from earning.