I agree with wolfie, but would add my own spin on it.
I started with carboys, until I had too many.
I then moved to demijohns, until I had too many,
I then switched to VC SS Tanks, and now I have too many.
I have been using VCSS tanks for the better part of 20 years for secondary fermentation and bulk storage. I have been using 200, 300, and 500 liter tanks and have had very good results with all three.
In looking at tanks, the best one to purchase is the one that has the lowest cost per liter. This always seems to be 300 liter tanks for some reason. Make sure that any quoted price includes a stand, spigot, lid, pump, and gasket. Some times they will mark down the price, only to stick it to you on the other things you will need.
The biggest reason to go to tanks is SPACE! for example, a 300 liter tank will take up just about the same amount of floor space as 1 demijohn. Think about it, 1 demijohn's worth of floor space for almost 6 demijohns worth of wine!
Also, It is far more easy to clean, rack, and test a single 300 liter tank then it is for 6 demijohns. Everything, therefore, becomes a much more simple chore.
Also, Tanks are (more or less) indestructable. I can't say the same for glassware.
The down side to using tanks is that you can only make on kind of wine. If you have many carboys, and each has a different wine, then tanks will not help you.
Another down side is that you will be having "all your eggs in one basket". If a 300 liter batch should go south, then you will be stuck with a rather large amount of bad wine. In other words, tanks should only be considered by winemakers that are VERY confident in their abilities and want to make few varieties in larger volumes. I would go further and say that if you are experimenting with your winemaking, never do so with a tank. Experiment only with carboys to minimize your risk. Once an experiment is proved successful, then go ahead and apply what you have learned to a tank.
If you are currently at the "too many carboys" stage, I would recomend that you make the move to demijohns before going to tanks.
Sorry to ramble on.
johnT