What really makes a difference is not so much the device as several different factors.
1. Batteries - First off most basic devices are 3.7 volt devices out there. This includes the 510,ego, silver bullet mod with 18650 battery ect and any and all clones. There are numerous factors that play into voltage though. The mosfet batteries on the ego and the 510 battery are not lithium Ion. Usually you only get LiIon with mods susch as the 18650 battery.(Correct me if I am wrong here please!). This is important as quite a few of the non mod battery pv's aim to have a voltage that is as close to 3.7 volts as possible. There are posts around this site that shows most of these batteries actually perform closer or under 3.6 volts. So less energy to feed the system. Also, the LiIon batteries do not have as great of a drop off as the 510 and ego style batteries over time, ie you vape at a more constant voltage for a longer period of time with a mod battery such as the 18650 batteries. This is the difference between a silver bullet mod that uses 18650 LiIon battery and an ego or 510, voltage will not decrease rapidly over time.
Another smaller thing to consider is Mah or milliamps per hour. Generally this determines how long your battery will last before it has to be recharged. But, also it determines how long you get a decent voltage before the performance is affected. If you vape on a 510 which is around 200 mah it is not going to get the atomizer as hot as an ego with a 750 or ego T with a 1100 mah rating. Also the battery life is really short.
2. Heating Element (atomizer) - This really boils down to personall preference and can have allot to do with flavor. An important value here is resistance. The lower the resistance the more heat is produce. Most standart atomizers have a resistance between 2.5 and 3 ohms of resistance. With a 3.7volt device that is not LiIon that means you have 4.2 to 3.8 watts of power if the device is running around 3.6 volts. If you go with a low resistance atomizer you start to get higher wattages that give you more heat. Most of these range from 1.5 to 2.0 ohm translating to 7.7 to 5.8 watts of power to the atomizer. The low resistance atomizers are supposed to give you a truer to 5 volt experience which is closer to around 8 watts.
The amount of heat applied to juice can greatly affect its flavor and that is what both battery and atomizer boils down to.
Here is a handy chart that somebody else on this site posted (sorry if I stole your chart) that greatly shows the relation of the battery/voltage to atomizer resistance in overall heat production.
3. Juice delivery method- Another factor that affects juice flavor is how it is delivered. Cartridges use a single atomizer and a cartridge stuffed with batting that you fill with liquid. When you push the button the atomizer heats up and cooks the juice in the batting turning it into vapor. The batting reduces some of the flavor in this method.
Another popular method is to use cartomizers which is a unit that contains an atomizer and some sort of batting or way of holding the liquid. This is probably the most popular method of vaping as it is easy to fill and gives a good amount of flavor and vapor. Cartomizers like most things with vaping comes in various flavors(such as dual coil, single coil) and resistances.
The most direct way is to drop a couple of drops onto the atomizer, put on a drip tip and vape directly off of the atomizer. Some claim this provides the best taste and more realistic heat. There are probably other things I have left out here, but that is the basics.
4. The juice itself - Juices come in basically two types - PG and VG. There are some hybrid mixtures. PG is usually thinner and sweeter where VG is thicker and produces more vapor. PG/VG can greatly affect the way the juice tastes on its own, but also they can affect the flavor based on the delivery method used. Some mixtures work and taste better with cartomizers and others dripping. It really all depends. This area I am still delving into, but I have seen allot of talk on this forum about the taste of juice in relation to delivery method.
So what does this all boil down to? Basically, you really need to try allot of different things to really figure out what works for you. I think understanding some of this stuff is helpful in determining that perfect sweet spot when it comes to juice. The hardware really is just that... hardware. The above factors will really have a larger effect on the taste of the juice more so than the device used.
Hope this helps, I am open to criticism if I got something wrong here, I have only been at this a very short period of time
