The Side Arms HuCard has everything visually that the arcade port on Side Arms Special does, as well as most of the arcade perfect sounding sfx. But I believe that there are a few extra digitized effects in 'Special. The Before Christ mode has entirely redrawn graphics and different bosses. The gameplay is kinda different and the weapons aren't all exactly the same. Its basically a remix of the original. The CD soundtrack alone makes Side Arms Special a must own even if you already own the HuCard.
The inclusion of a CD soundtrack might sway me a bit. I was under the impression the CD just recycled the chip music.
You can find the HuCard for a pretty good price, I'd reckon. Get that if you want to play it safe.
However, I would definitely recommend getting the CD version. Nice soundtrack + BC mode = great deal.
I still play the HuCard when I want to hear some chiptunes... so you can't lose either way.
And, quickly... R-Type complete... I agree with B_T: the cinemas aren't anything to get excited about (sad but true). The soundtrack is interesting simply because it doesn't sound like a generic re-hash of the classic tunes. If you are a big R-type fan, then get the CD for the novelty of the redbook alone, if nothing else.
Super Raiden: search these forums for rolins + Super Raiden. He made an exhaustive comparison of the HuCard vs. CD. My advice is the same I gave you for Sidearms: get the cheap HuCard first, but you won't be disappointed by the CD. TWO extra levels in Super Raiden, plus a TRULY amazing redbook soundtrack that is faithful to the HuCard but still manages to impress. R-Type Complete redbook might not be everyone's cup of tea, but Super Raiden
will not disappoint fans!
And, since I know that you are a definitely going to buy Jack Nicklaus Championship Golf, go for the CD version!