Paintball markers come in many different designs and can fire at many different rates of fire and with different degrees of accuracy. You should choose a marker that is best for the type of paintball that you wish to play and for you own personal technical ability as some markers require more maintenance than others.
Blow back semi markers
The blow back semi is the default starter marker and is the type of mechanism that is employed by all leading entry marker brands including the H18 Eros, all Spyder markers, PMI Pirhana etc. The blow back semi is the most reliable type of system and requires very little work to maintain it. These are the ideal paintball gun for beginners.
Blow back electronic paintball markers
The blow back electro is a variation on the blow back semi but it has limitations. Basically a standard blow back marker is fitted with an electronic frame which allows significantly increased rates of fire. The downside of these markers is that often at high rates of fire they will break paintballs and can ‘freeze up’ when used with CO2. This type of paintball guns are a significant step up from blow back semis.
Spool valve markers
The spool valve marker is a relatively recent development and has made very high performance markers a lot cheaper. Spool valve markers are very gentle on paint and as such make excellent tournament markers however they require quite a lot of maintenance as paintball guns go. You should really take the bolt out of the gun and clean and re-grease it every time it is used although most players only do this before a big event of every 3 or 4 uses.
High end markers
The build quality of a paintball gun is again generally related to the quality of the materials used to make it. The higher the grade of materials the more ability the manufacturer has to make high quality parts that will withstand diving and intense tournament paintball play and the more reliable your marker should be at high rates of fire.