> But the fact that you can compare a Ferrari with a Russian truck
> doesn't mean they compete, or that one is better than the other. If
> you want to haul gravel, you choose one. If you want to attract gold-
> diggers, you choose the other.

True at a features level, not true at a general level, imho.

- Products are not as different as the analogy suggests: perhaps saying
that the comparison is between a 7-series BMW and a X5 BMW is more
appropriate. Very different cars, yet they compete, because they
overlap in price, status, etc. Same for databases, they overlap.

- All products compete for the buyers attention: if the golddigger has
not heard about Ferrari, not absorbed its (marketing generated) image,
not heard friends admire it, he won't buy the Ferrari. If all people
talk about is Russian trucks, then he/she will buy a Russian truck with
fancy leather seats.

- All products compete for the same money (time): if the golddigger is
owner of a gold mine, he/she may need both a Russian truck and a
Ferrari, yet be able to afford only one. The products are very
different, but the gold digger/miner has to choose which one to buy
first.