As a guitar (and effects) nerd, I feel obliged to step in here. Boss effects are sturdily built and sell very well, but they are hardly the best. The hating on Dano minis is especially ridiculous. They're probably the best bang for the buck pedals out there. Period. Try the Tuna Melt, PB&J and French Toast if you doubt me.
As for pedals vs. a good amp, they're completely different beasts. A good tube amp's overdrive will be smoother and richer than a distortion or overdrive pedal. But put an overdrive in front of that amp, and you'll push it into some of the best lead tones possible. And, of course, no pre-amp can give you delay, chorus, flanging, or other crazy effects. Which segues nicely into:
Different Types of Effects and Their Uses
Overdrive, Distortion, Fuzz
These are all lumped together because they all do the same basic job- clip the signal, giving you a "distorted" sound of some sort. All together, they're by FAR the most common type of effect. But they're all used differently. Overdrives give a volume boost and some light grit to your tone that's perfect for pushing an amp into a sustaining, saturated lead tone. Distortion pedals give more dirt, and are good for heavier sounds. Fuzz is a bit harder to explain, but the name does a good job. It's a very distorted sound, without all the "heaviness" you get from lots of normal distortion. Lots of fun.
Time-Based Effects
Ever said anything in a raquetball court? Or shouted in a bathroom? You know how the sound takes a second to fade out? That's reverb. Good for adding some warmth and smoothing out your tone. Delay, on the other hand, adds to the original signal a copy of it, delayed some. The amount of time the signal is delayed and the number of repeats depend on your settings. Very short delays are often used like reverb, and longer delays can make sweet echoes. See half of U2's back catalog for good examples of echo use.
Modulation
This is probably the braodest category, and possibly the least common, so I'll be pretty brief with each kind. Tremolo (not to be confused with a guitar's tremolo bar) modulates the volume of your signal. Much more common with electric organ than electric guitar, but don't let that stop you. Vibrato modulates the pitch of your signal. True pitch-shifting vibrato pedals are hard to find, alas, but they're out there. Phasers and flangers both are complicated to explain technically, so I won't. To get an idea of what they sound like, sing a note and open and close your mouth as you hold the note.
EQ
EQ pedals boost or cut different frequencies within your signal. Good for shaping your overall tone, or to switch on a boost to volume and midrange frequencies to help solos stand out of the mix. Wah pedals are a variable midrange boost, and the foot pedal controls what frequencies get boosted. THE classic example of wah use is Voodoo Child, by Hendrix.
And that is a basic overview of guitar effects. There's a whole crapload that can still be said about them- my best advice is to start with a multi-effects unit and then start playing around with different pedals. Don't discount any pedals, no matter how random or cheap- they all have their own sounds and features, and you never know which is right for you.
