What do you suggest and why?? Use a normal network card or a server edition
for example 3Com 3C980C-TX-M Etherlink Server 10/100 PCI or the 3Com 3C905C-TX-M FastEtherlink 10/100 PCI

What is the advantage of the server card, most of the time they are more expensive, but i don't see why.

Have you been to 3com's site?

1. Better warranty
2. More feature rich software (which may or may not be useful to you depending on if the software and drivers are available for your OS).
3. Possibly smarter I/O logic.

The software allows for failover and more intelligent network functions like load balancing. You should probably just visit 3com's site and see if you need the extra features and if it'll work on your OS. If it is actually for a $10,000+ server you might want the extra features. But for just a web server or something you probably don't need it.

I recommend Intel network cards over 3com though. And for most cases, a Realtek 8139 chipset will do just fine.

But maybe you'll get some more opinions on this thread.

Well, i heard some people being not too positive about realtek chipsets, i personally don't have problems with it.

But is a 3com or intel chipset faster. I believe 3com has something that it's allows the chip to send already while still receiving(something realtek isn't able to do). Will give this a noticable differents in performance.

And what about intel
Also, my servers run linux redhat. I don't install additional load balancing software of some kind, so i don't think i need the server edition.

You should check out Tom's Hardware Guide's comparison:

http://www4.tomshardware.com/network/01q3/010820/index.html

Although the problem is that they didn't compare a realtek chipset, or bidirectional transfer or on UNIX.

They picked 3com over Intel, and the 3com card does show that it can outperform an Intel card in both throughput and PCI bus utilization.

However, my issue is the whole problem with different mods of 3com cards not working under Linux with certain drivers. This may have finally been corrected as 3com finally released their own drivers, and we no longer have to rely on the open source community to hack some drivers without help from the vendor. But I haven't gotten around to testing it, and probably never will. That's why I prefer Intel over 3com.

Intel and 3com will outperform a realtek card, but unless you're using it on a LAN, you aren't going to be able to use even a realtek card's maximum throughput on an Internet connection. And realtek has good latency ratings in benchmarks. I've never had a problem with realtek cards and have been using them since the 8129 chipset at home and at work. Would I put one in a fileserver if I could afford an Intel? No. Would I put one in a web server or a workstation? Yes.