Engine selection is probably has the single largest factor affecting the the performance of the Bearhawk. It also has a very large effect on the empty weight and CG of the aircraft, and hence the useful payload. This is a case where bigger isn't always better, there's a definite compromise, particularly when operating in the back country. For a simple comparison below, I discuss a Lycoming IO540 vs a Lycoming IO360.
The Bearhawk 4B MTOW is stated as 2700lbs. I've tested mine to this weight. However I was concerned about damage to the airframe, so I use 2500lbs as a MTOW and if operating on short or rough airstrips I restrict it further to a maximum of 2200lbs.
Effectively for a backcountry machine it becomes a very capable 2 person aircraft - or 3 persons in the right conditions. On a longer grass runway it's a capable 4 place machine.
In addition to the load carrying capacity, the aircraft also needs to have sufficient CG range to carry that weight in order to be useful.
Useful Load and CG My Bearhawk has an empty weight of 1500lbs (this appears to be a very typical average weight with an IO540), and an empty CG of 10.5". That's a very forward CG (the 3 bladed prop contributes to this). This coincides with the forward CG limit (also 10.5"), so with one pilot and reserve fuel, mine is nearly on the forward limit. This gives maximum utilization of the full CG range (10.5" - 22.5"), and at a MTOW of 2500lbs it gives a useful load of 1000lbs.
An IO540 powered Bearhawk usually becomes limited by the maximum landing weight before it reaches the aft CG limit. For a Bearhawk with an IO360, a typical empty weight is 1300 - 1350lbs (some are built even lighter). That's roughly 150lbs lighter than mine. If using a MTOW of 2500lbs (as I do on mine) that same aircraft will have a payload of 1150lbs.
Looking at it another way, it could use a MTOW for backcountry ops of 2200lbs and have a useful payload of 850lbs. Or it could utilize the same payload that I restrict myself to for backcountry ops of 700lbs, and have a TOW of only 2050lbs. This gives lower takeoff and landing distances and is very airframe friendly. Whichever way you look at it, there's a clear advantage.
Due to the lighter weight of the engine, an IO360 powered Bearhawk may have an empty CG of around 16" (giving it a useful CG range of 16" - 22.5").
The IO360 powered Bearhawk tends to be limited by the aft CG limit before it reaches maximum takeoff weight.
Takeoff and Landing Distance
Take-off and Landing distances tend to be very similar, for the same payload. The aircraft with less horsepower also tends to have a lower takeoff weight for the same payload (lighter engine).
If operating at the same takeoff weight, then the aircraft with more horsepower will outperform one with less horsepower. But in this case, the aircraft with less horsepower is also carrying approximately 150lbs more payload. This factor can often be overlooked.
The IO540 is a clear winner in climb performance.
If both aircraft are cruising at the same speed, they both tend to have a similar fuel flow. The main difference is that an IO540 powered aircraft will have a higher top-end cruise airspeed available, if desired. That said, in practice, I seldom use the higher cruise speed available, opting for a more wallet friendly pace of life.
Under the cowling
An IO360 installation leaves significantly more room behind the engine for access and accessories. It's just much easier to get to everything.
Any engine with more cylinders is going to have a higher cost of maintenance over the life of the engine.
Having a large engine up front means when operating at light weights I am often near the forward limit of 10.5". Any time the Bearhawk CG is forward of 14", it tends to lose elevator authority when at approach speeds below 55kts. This can be mitigated by keeping the power on to provide airflow over the elevators, or by increasing the approach speed. It's something to be aware of, but you do get used to it.
With a lighter engine, the CG is naturally further aft so elevator authority doesn't tend to be an issue.