1) Character Slots
Pve and Pvp are both big parts of guild wars. Everything considered, I'd give them both about 50% of the game (Pve has a bigger size, but Pvp is far more versitile. Playing different professions in Pve does not change general strategy THAT much, whereas in Pvp it's a world of difference.)

Most players start off by filling all character slots with PvE only characters, because they can participate in PvP; and PvP only characters cannot go to PvE. This makes some sense, but is quite futile.

The advantage of PvP only characters is that they only require a single slot. 1 single slot unlocks the entire world of PvP for you IMMEDIATELY, for ANY profession. Getting a PvE only character to PvP would take WEEKS till MONTHS to play only ONE profession.

2) Advantages of PvE only characters in PvP
*It's easyer to acquire pretty looking weapons in PvE. In PvP, you have to win a lot before you can unlock special skins.

3) Advantages of PvP only characters in PvP
*You start off at lvl 20. So no days of training to get to lvl 20
*Your armor is always at maximum level, and is freely customizable once you unlock the runes. So no need to invest money in armor, nor in runes (a rune of Sup Vig is a must in just about every PvP build). This also means you don't have to pay money every time you need to change your armor's runes (which is very frequently in pvp).
*Your weapons and offhands are perfect and customized, and freely customizable once you unlock the runes, which also means you'll save quite some money here. (50k ish considering most pvp builds benefit from having multiple weapon sets).
*Equipment (armor + weapons/offhands) can be saved and loaded quickly, just like builds. This means that you don't even have to spend time in equipment .
*You can use all skills that are unlocked on your account. This means every skill any character ever acquired from a skill trainer (for money), from a hero skill trainer (for hero skill points) AND from a priest of balthazar (for factions).

3) Flaming
You must be warned that bringing a PvE only character to PvP is a reason for flaming in the PvP world. Often, players from PvE are looked down upon in PvP. This is mainly because a PvE only character CAN be as good in pvp as a pvp only character (after several weeks and over 100K of investment), but in reality, only about 5% of PvE only characters are good enough in PvP to last.

4) Summary
Taking 1 pvp only slot saves you several weeks till months of training and a minimum of about 100-150K for every time you play another profession. All you need to do with a pvp-only slot is delete the character and create a new one which is immediately at full strength and in the posession of all possible items.

guess im one of the 5% then

You do pvp a lot?
We should do some TA or HA mate ^^
Anytime you want