Well, the first thing you will notice will be drastically increased power. The EVOs are pretty hot. Next, clarity will be much better. The EVO has a lot of mids and presence, and are great at overdriving an amp for solos AND for heavy rhythm. String seperation and definition will be greatly improved. It should be a drop-in replacement.
If a pickup is passive, then it's a normal pickup that used 250k-1 megaohm pots, and produces a high impedance signal. Active pickups incorporate s small preamp inside the pickup, and produced a low impedance signal. They typically use around 25k pots. The typical active example is the EMG line of pickups. They require a battery. Some people swear by them, and others avoid them like the plague. I tend to fall into the latter category, but don't let that influence your decision. The main attraction of active pickups is the extremely high output, which is actually completely unnecessary, but the companies advertise them like output is all that matters. Active pups are generally much more of a pain than passives, as it takes just short of a minor miracle to get them to work with passive pickups on the same guitar. You pretty much have to go completely active, which severely cuts down on your options. A great product is the EMG Afterburner. I have one, and it converts the signal to low impedance and provides a boost of up to 20dB, and works with active or passive pickups. With passive pups, it gives you all the benefits of active pickups with very little hassle. You have to change the battery about once every year, but that's it.