This is an area of controversy. Many have run standard servos for years, and state they've never had a problem. Others state anything less than top/near-top of the line is a failure waiting to happen. In my opinion: standard servos are fine for Bronze; Higher-quality servos are a morejustifiable investmentfor Gold; but a good medium-quality ball-bearing servo will serve you well in Silver.

After a couple of unexplaned failures when usingstandard servos, I have gone the digital route, but still try to keep it reasonably inexpensive. The JR DS821 is a decent quality, readily available servo, for about $30 each,that would likely do well for you all-around. However, I also received a bunch of JRDS537 servos in some flight packs I bought a few years ago. Beings these have a little lower torque than the 821s, I use them in lieu of 821s for individual aileron servos. For the rudder, where I think a little more holding power is adventageous, I definitely use the DS821. Beings the elevator is likely undergoing the most strain (and I have lost my elevator control in a turn and found a stripped gear after the crash), I have begun to invest a little more for this servo. For elevator control, I am currently using an Airtronics 94162 digital high-torque, ball bearing, metal gear servo that comes out-of-the-box with a heavy duty control arm. These are available through Hobby People.

The picture below shows my current rudder and elevator setup forthe "Trinity-build" P-51 project I am currently working on.
And "YES" Skids, I DO realize that my servos are not actually screwed-in, nor are my linkages actually connected. Like my fuel tank, this is just a trial-fit.
(I just know you'd find a way to tease me about this, if I didn't "nip it in the bud", first. )

As you can see, I also prefer using carbon fiber rods toensure free-moving, yetflex-free linkages, withoutall the hassle of more carefully laying out an extensive internalbracing structure.