They are 2 different products.
Kaspersky Antivirus 6 (KAV6) is a dedicated anti-virus product. It does not include a firewall or anti-spam applications. KAV6 now looks for spyware/malware (dialers, adware, joke apps, etc..) as well as rootkits (if set up accordingly).
Kaspersky Internet Suite 6 includes KAV6 plus Kaspersky's Firewall (Anti-hacker) and their Anti-spam products.
Both are available as trial apps (30 days) at the Kaspersky site:
http://usa.kaspersky.com/products/
Other good fee options (i.e. not free) include:
- F-Secure (uses the Kaspersky AV engine and Lavasoft Adaware engine, has rootkit detection)
- NOD32 (Pure AV, fast and compact, great heuristics)
- Bitdefender (Good AV, great heuristics)
All offer trials. I'd recommend that you nose around and look at some reviews, and try the applications out. Try the features, and find the right app for you.
With the suites, make sure the firewall does what you want it to do, and it can pass stealth/exploit tests (try
www.pcflank.com for some probe tests). You may find that it is better to buy an AV from one company and use a firewall from another.
I personally use KAV 6, and it think it is great. I use Sunbelt Kerio as a firewall which is also great. But that's just me, find the right app for you.