In the end it's up to you, but from my playing with Dwarves, I find that pistols aren't of much use except on your Noble, who gets a shot every now and then. Pistols for Henchmen just doesn't seem worth it, though I have yet to try Pistol/Spear combo, which actually doesn't sound too bad (in our rules, where Spears are strike first, disregarding Initiative).
My own way of playing Dwarves is a lot of Thunderers with WS5 BS4 S4 A2, if I'm that lucky. I provide them with Crossbows and just put them where I can maintain some steady shooting. It varies with the scenario how effective it is, but else I just put them into melee, where they still hit like trucks. No matter what, I'd still argue that Dwarves is one of the best warbands, if you keep your Heroes back in the beginning. This is also why I recommend going long range, since that's what their speciality is. Against shooting, they're only taken out of action, if they're even hit, on 5+ followed by 1, 2 or 3 followed by 6+ (2,7% chance) if shot by a Bow/Longbow - and that's just the henchmen. An Engineer with T5 and Gromril/Shield would only be taken out on 6+ followed by 1 or 2 followed by a 6+ (1% chance). All in all, low chance. Of course, Crossbows hit dwarves hard as well, but without Hunting Arrows, they're still hard to actually kill. On top of that, add a Helmet save, ensuring that they can get up and shoot back the next round.
My tip though - don't climb up with them. Had a game two days ago, where I tried climbing for the fun of it. Somehow I managed to climb 6" up over 2 rounds with 3 Dwarves at I2. But when they got knocked/stunned and fell down, one of them weren't so lucky - fun to watch two Dwarves fall 6" though! One of them died permanently, the other got KD.
So anyway, I'd stay back and hail some bolts over the enemy. It takes a bit of positioning, but after some time, you'll find the weak spots. Against other shooters, you won't have a problem, since they'll have to see you in order to shoot - so you just shoot right back!
Also, bear in mind, that with positioned Crossbows and BS4, you'll hit on 4+/5+, while with Pistols and Dwarves, you'll usually have to move, and the enemy is behind cover and most likely long range. With BS4, that's 5+/6+. It evens out if the enemy has a 5+ save or better, but against non-armoured opponents, the Crossbow is better.