Even just five years ago, the differences between hardtails & full-suspension mountainbikes in terms of climbing/pedalling efficiency were pretty large. Suspension damper technology wasn’t nearly as advanced as it is now, and suspension designs (linkage location & pivot placement) were pretty basic, with there being four standard setups; VPP, Horst-link, single-pivot, and four-bar, with DW-Linkages being developed more recently.
Of those four, VPP & Horst-linkages had the greatest impact on climbing/pedalling efficiency; VPP aided the most on climbs & sprinting, while Horst-linkage bikes are, for the most part, happily immune to pedal feedback over rough terrain.
Single-pivot & four-bar depend a lot on what type of damper is being used, and benefitted the most from shocks equipped with compression & rebound adjustments, and some sort of lock-out or pedal-input damping (i.e. "ProPedal"). Single-pivot/four-bar designs also had a greater amount of inherent structural strength, while some of the original VPP & Horst-linkages were flimsy & prone to structural failure.
But new full-suspension bikes of all types have been refined a lot, eliminating most of the teething problems that the more complex suspensions suffered from. Suspension damper technology has advanced by leaps & bounds, and while once found only on high-end shocks/forks, the more complex adjustments are now being used on more entry-level dampers.
But even with the newest shocks/forks, there are still basic attributes that are unique to each suspension design.
Here’s my rundown on FS bikes, their pro’s & cons:
Singlepivot (i.e. SantaCruz Heckler, Cannondale bikes)-
These bikes are great in their simplicity, strength, and versatility of design. They can be built either as a minimal travel XC race bike, or a freeride meteor. However, they do suffer from pedal-bob, and the suspension is often locked out while pedaling or braking, making the bike a virtual hardtail. This can be alleviated to an extent by many of the pedaling-platform shocks on the market, as well as several aftermarket floating-brake caliper setups.
Horstlink/FSR (i.e. Specialized FS bikes, Norco bikes)-
This suspension design is considered one of the best pedaling, and remains fairly active under braking. However, it can be somewhat flimsy unless well designed, and companies other than Specialized have to pay to use their patent, and often that shows in the cost of a Horstlink bike. Norco is a company that makes a killer DH rig using this setup.
Virtual Pivot Point (i.e. SantaCruz Blur, Intense bikes, Marin bikes)- Here the rear triangle pivots on two short rotating links near the seat-tube, and behind the bottom braket. This design is very versatile, but depends a LOT on proper shock setup/sag. When done correctly, these bikes resist pedal-bob very well, and although they do exhibit some stiffening of the suspension under braking, it’s negligible. Again, this depends highly on proper shock setup.
Four-bar/Rocker Link (i.e. Trek bikes, Kona bikes)-
This is design is very similar to the FSR/Horstlink setup, but differs in that the rear pivot is placed above the axle instead of on the chainstays. This makes causes a small increase in pedal-bob, but has more of a tendancy to lock-out the suspension under braking. However, these bikes can be made as light or as beefy as needed, and there are a lot more choices of frames using this design.
DW Link (i.e. Iron Horse bikes)-
This is a fairly new design, somewhat related to the VPP linkage system, but supposedly responds a lot better to hard pedaling than the VPP suspensions and is not as reliant on precise shock dialing. I’m not too familiar with this setup, other than what I’ve read.
I-Drive/Freedrive (i.e. GT bikes, Mongoose bikes)-
These look a bit like a singlepivot design, except that the pivoting rear triangle actually includes the bottom bracket. This solves the problem of pedaling toping out the suspension, and pedal bob to some extent. I am unfamiliar with this design as well, and I am unsure on how braking affects this suspension.
Soft-Tails (i.e. Salsa bikes)-
These have a very minimal amount of travel, and this is granted by the seatstays actually flexing up to 2", and damped by a shock. I’ve seen this setup on a lot of 29" bikes, and are popular with the XC/endurance crowd. The bonus here is that the price of a premium softtail frame is often between that of a hardtail and a full-on FS rig, and while not providing as much cushion, they still keep you from feeling every bump later and are simple to service.
"Magic-Link" (Kona’s new design)-
Now, this one is VERY interesting. Under power or while coasting, and depending on the rider’s position, the extra little shock under the main damper compresses or extends. This changes the bike’s headtube angle, making it steer slower on fast downhills or sharper on climbs. It also increases/decreases suspension travel a bit. I’ve not tested this design out yet, but from all accounts it’s a very effective & efficient suspension.
ABP ("Active Braking Pivot")- Another new design, this one puts the rear pivot point at the rear axle, which supposedly does away with braking/pedalling feedback. Again, I’ve not tested it, but it is also reported to be very good.
So pick your poison….
I will say that as far as FS rigs go, you really do get what you pay for. Not that $5000 means you get a perfect bike, but around $1500-2000 will get you a pretty reliable and versatile bike with a good component group.