I joined Blue because as a new player to the game, the server was almost brand new at that time, as well. Not only was I able to not be behind over a year in terms of progress within the server like I would have been in Red, but I was able to afford items and pokemon at a reasonable price a newcomer such as myself needed. Since then, as more players and money have entered the economy alongside all the items and pokemon, the values have significantly heightened.
A prime example is the membership medallion. Beginning on Blue, it had been around 100k. Today, it peaks at 4x that as more players can afford that and even the supply has lowered. This is not to say that new items within the shop have not affected the price, but you would think the price would die down alongside the hype - which it has not. Coincidence? Possibly.
I recommend you do join Blue, nonetheless a bit biased.