The person who's going to be wielding the bow in a GURPS fantasy setting is more than likely only going to have a ST of 12.
Let's shoot Smedley The Orc, wearing DR 4 scale in the chest and see what happens!
All bows have a RoF of 1 and Shots 1(2). That means one shot every three seconds.
Longbow, $200, 1d+1 imp, 180/240; 2-7 raw, 0-3 penetrates, 0-6 damage (average of 0)
Regular Bow, $100, 1d imp, 180/240; 1-6 raw, 0-2 penetrates, 0-4 damage (average of 0)
Short Bow, $50, 1d-1 imp, 180/240; 0-5 raw, 0-1 penetrates, 0-2 damage (average of 0)
Reflex Bow, $900, 1d+2 imp 240/300; 3-8 raw, 0-4 penetrates, 0-8 damage (average of 2)
Straight Composite Bow, $600, 1d+1 imp, 180/240; 2-7 raw, 0-3 penetrates, 0-6 damage (average of 0)
Smedley is feeling good about his chances.
OK, how about crossbows? All are RoF 1. All are $150!
ST 12 Crossbow Shots 1(4), 1d+3 imp, 240/300; 4-9 raw, 0-5 penetrates, 0-10 damage (average of 4)
ST 14 Crossbow using one leg on the stirrup or a belt-hook $25 (Shots 1(5)), 2d imp, 280/350; 2-12 raw, 0-8 penetrates, 0-16 damage (average of 6)
ST 15 Crossbow using both legs on the stirrup Shots 1(5), 2d+1 imp, 300/375; 3-13 raw, 0-9 penetrates, 0-18 damage (average of 8)
ST 16 Crossbow using a goat's foot $50, Shots 1(22), 2d+1 imp, 320/400; 3-13 raw, 0-9 penetrates, 0-18 damage (average of 8)
ST 18 Crossbow using a 1.5x windlass $55, Shots 1(16), 2d+2 imp, 360/450; 4-14 raw, 0-10 penetrates, 0-20 damage (average of 10)
ST 24 Crossbow using a 2x windlass $100, Shots 1(23), 3d+1 imp, 480/600; 4-19 raw, 0-15 penetrates, 0-30 damage (average of 14)
ST 30 Crossbow using a 2.5x windlass $155, Shots 1(32), 4d imp, 600/750; 4-24 raw, 0-20 penetrates, 0-40 damage (average of 20)
ST 36 Crossbow using a 3x windlass $225, Shots 1(43), 5d-1 imp, 720/900; 4-29 raw, 0-25 penetrates, 0-50 damage (average of 32)
Steel Crossbows, which are TL4 like most early guns.
ST 18 Fowling Crossbow, $450 using a 1.5x cranequin $55, Shots 1(25), 3d-1 imp, 225/270; 2-17 raw, 0-13 penetrates, 0-26 damage (average of 11)
ST 24 (2) Hunting Crossbow, $600 using a 2x cranequin $100, Shots 1(39), 3d+1 imp, 300/360; 4-19 raw, 0-15 penetrates, 0-30 damage (average of 15)
ST 36 (3) Military Crossbow, $750 using a 3x cranequin $225, Shots 1(79), 5d imp, 450/540; 5-30 raw, 1-26 penetrates, 2-52 damage (average of 27)
Smedley is less enthusiastic about crossbows, but the lower rate of fire means he's got a better chance of not getting hit twice.
Now long guns!
Gonne Shots 1(30), 2d+1 pi++, 55/550; 3-13 raw, 0-9 penetrates, 0-18 damage (average of 8)
Matchlocks
Arquebus, $150, Shots 1(60), 2d+2 pi+, 65/660; 4-14 raw, 0-10 penetrates, 0-15 damage (average of 7)
Caliver, $135, Shots 1(60), 3d+1 pi+, 85/870; 4-19 raw, 0-15 penetrates, 0-22 damage (average of 11)
Musket, $175, from a rest, Shots 1(60), 4d+2 pi++, 120/1,200; 6-26 raw, 2-22 penetrates, 4-44 damage (average of 24)
Wheellocks
Carbine, $290, Shots 1(40), 3d pi++, 80/800; 3-18 raw, 0-14 penetrates, 0-28 damage (average of 20)
Wheellock Pistols
Military Pistol, $250, Shots 1(20), 2d-1 pi+, 50/500; 1-11 raw, 0-7 penetrates, 0-10 damage (average of 3)
Petronel, $280, Shots 1(40), 2d+2 pi+, 60/630; 4-14 raw, 0-10 penetrates, 0-15 damage (average of 7)
Pocket Pistol, $190, Shots 1(20), 1d pi, 25/300; 1-6 raw, 0-2 penetrates, 0-2 damage (average of 0)
Puffer Pistol, $260, Shots 1(20), 2d-1 pi+, 50/550, 1-11 raw, 0-7 penetrates, 0-10 damage (average of 3)
Bows are not so great against DR 4, so you want something with more pussiance, but the rate of fire falls off fast.
Remember! An English longbow is a ST 17 item that does 2d imp, 255/340; 2-12 raw, 0-8 penetrates, 0-16 damage (average of 6); when you read about bows in most histories this is the benchmark.
Likewise, the average crossbowman was a peasant levy with a ST of 10 using a ST 13 crossbow using both feet on the stirrup doing 2d imp, 260/325; 2-12 raw, 0-8 penetrates, 0-16 damage (average of 6)
Adventurers are different from historical people!