The short answer is try it out to see how it sounds. A well-designed older gate will certainly outperform a new bargain piece. Spend some time with it if you can, especially if you have never used gates before. They can take a little getting used to. Just like compressors, badly designed or badly set gates can "breathe".
Gates are tricky technology, and good ones are expensive. Some cheap ones are good, too. It's kind of luck of the draw with cheap ones, though. I have an old Furman 4 channel that works pretty well.
A few things have changed. Modern gates as a whole open more quickly, with some even having "look ahead" circuits to open a microsecond before the signal starts. There are usually more controls, not just attack, release, and ratio, like my Furman
. Hell, some old ones just have threshold. Many can be set to react only to a specific freq range, like you set the kick gate for 80-100 hz and it will only open when the kick drum is hit, and will ignore the cymbals and snare. Gates without this feature will open at a specifc signal level, regardless of frequency. So for kick and snare, you have to gate harder so your kick gate doesn't open when the snare gets hit.
That being said, people did just fine without any of those features for a long time. If it works well, it works well.
Another thing these days is that since two-channel gates are so full-featured, with multis you usually give up some control. Again, ten years ago, no gates had the controls they do today.
Listen to make sure transients don't get cut off on sources like snare drum. Less well-built gates open slowly, and may cut off the first part of the signal. For live work, this is usually OK, and can even be used as a tool, but for recording it is annoying.
Listen to see that there is no "click" as the gate opens. This is a trademark of poor gate design. Don't confuse the abrupt change in sound level as the gate opens for a click. It will be a definite "click". Then you have to try to get rid of that. It's a vicious circle.
Buying DIY gear is tricky. I wouldn't even want to guess at a price. But be prepared to sell it at a loss, if you do sell it. On the other hand, if it works well, you may end up keeping it for many years, like the guy who built it.
12 channels is a lot!
That should keep you well-gated. You can probably get 4-6 channels of name-brand gates for the same or a bit more than the 12 channel dealie. They won't have much more resale value, though.
Personally, I've never needed more than 6. YMMV.
Some other multi-channel options, and cheap two-channels:
(I have a behringer intelligate and an old four channel Furman, BTW)
Presonus ACP-88. Gates are reasonable, compressors are awesome. Gates have minimal controls, and are tricky to tweak. Sound good once you are there, though. No frequency setting, but there are sidechain inserts for an eq or freq plug. No hold control for the gate, which is a control I personally like.
ARX six gate. Heard pretty good things, hard to find in the US, no idea about price.
Rane Quad4: Very good reviews! Four completely featured channels in two spaces. Suposed to be awesome. Better be, for $800.
Drawmer and BSS four channels. Very good, much money.
Behringer Intelligate. Two channels, all the goodies, pretty quiet & fast, $125 new.
Aphex 105- 4 channels, all controls but freq. You can insert an eq to do this, though, or make frequency plugs. More spendy than behringer multigate, but nicer.
