Changing my gearing

You must not own a calculator! 🙂

50/11 is actually slightly taller/faster than 53/12, so you will have a slightly higher (theoretical) top speed.

And certainly your lowest gear 34/28 will be very decent on hills, almost (but not quite) as low a gear as most bikes with triples have (i.e., with a triple and a more typical 12-25 cassette, or 30/25).

So if your crank change can be done with just a spider and chain ring change, then it looks like a good plan.

Actually, you might want to just change the crank to the compact double first, and see if you are OK with your existing 12-27 cassette. You will only be giving up a little bit of top speed, and a little bit at the low end, but you might actually prefer the somewhat tighter gear spacing.

Your rear derailleur is probably OK as is (probably a short-cage, I assume), although you might not have quite enough reach to use the extreme cross-chain combinations. And maybe you will have to take a link or two out of the chain. Older Shimano RD's might not be compatible on paper with a 28-tooth large cog, but I think this usually works (and since you already have a 27, it almost certainly will clear).

Moving to a compact charing setup, would mean that you have to get a compact crankset. The bolt diameter is different. You cannot mix chainrings meant for standard cranksets with a compact crankset.

While you can get a 50T in 130bcd (standard bolt circle diameter), you cannot get a 34T in 130bcd.

There are many online gear calculators that you can use to get an idea of how many extra gears the compact crankset will give you on the lower end.

Don't forget to consider a triple, unless you have a double (only) left shifter. I changed to triple recently after quite some years on a double, and won't go back.

As Thomas mentioned, you cannot simply change the chainrings to go compact.

I made a change to compact and I haven't regretted it so far. It's fantastic. I like it even though I moved from a hilly area to a flat area because I really like the tighter gear ratios. It's actually faster than my standard set up because I have a 50/11 combo which is faster than a 53/12.

Even though you cannot use compact rings on a standard crank, I suspect you will eventually be able to use standard rings on a compact one day! I saw that Vinokourov had these special standard chainrings that were compatible with his compact crank. They are not available on the market now, but keep an eye out for it...in a couple of years they may be!