The two sides in brief, the current balance:
The Combine have better structure and communications, everyone has a radio - everyone is encouraged to get into VC (Though not required).
Combine have unlimited supply of:
Biogel and Batteries (Though can only choose to use one on the field, as per rules)
Ammo (9mm and 4.6mm)
Pouches/Bags
Anything else is limited in vendor (with a X/X indicator)
Combine have great support options, but are limited in the way they're deployed and can be used. Making them predictable.
The Rebels have the ability to be anywhere at any time, with individual equipment being more powerful and viable to what the Combine can wield outside of certain OTA Specializations. Rebels don't have the burden of 'Bureaucracy' getting in the way of their decisions, they can act on impulse and do shit - so long as they have the equipment.
Rebels are much harder to spot and detect, especially since they're usually in small groups.
Vortigaunts are a huge power modifier. With no ammo requirement and infinite range theoretically, they are feared by cops.
All in all, I'm having fun with the asymmetrical dynamic. It's the nice Balance of brief s2k and passive RP that I wish ww3rp had. People need to realize at the end of the day, it's just about the 'War Stories' people get to tell and you shouldn't get so worked up on the balance or the "Factions". So long as the server facilitates Roleplay - you can find enjoyment regardless of what character you play.