Harry_Bucknuts ,
there isn' t much difference in knockdown power . More folks don' t use them because the opportunities in most states are extremely limited . Predjudice from the archery community is the principle reason for this . Most of what folks think they know about crossbows is actually second hand from other folks who don' t own one at all . Properly used , a crossbow can take any game that a compound or other bow can , and anyone who thinks they' re easy to hunt with has never tried it . If it' s legal where you hunt try one . You can get an entry level 150# for around $100 , which will satisfy any state' s minimum poundage requirement .
As with a vertical bow , practice , practice , practice !

Gryan ,
you can get scopes and red dot sights for vertical bows now too , check Cabelas . As for a crossbow having greater range and being quiet(silencer) , don' t make me laugh ! The longest shot that I would try with my 150# Barnett would be 30 yards , the drop on a bolt can be breath taking . Quiet ? Even with string whiskers it sounds like somebody thumping a drum compared to a tricked out compound , and you can' t find much else to quiet them down other than string leeches . More accurate ? If you add a scope and sight it properly maybe , but don' t bet on it . If your string isn' t centered when drawn that bolt can go crazy . Crossbows also don' t shoot as accurately offhand as compounds from my personal experience .

Also , most of the manufacturers don' t reccomend leaving one " cocked and locked" for long , 3-4 hours tops in my case , because it can damage the prod(bow) . That means that I have to draw too or risk having a highly tentioned prod snap in my face . Try drawing 150# while the deer is looking , and then loading your noisy bolt , now that' s challenging ! One of the biggest objections to them from the archery community is that you don' t have to hold them at full draw , which is also why you can' t hunt with them in many states during archery seasons . What a friggin' crock ! How many of you bow hunters use a bow with 70% let off ? 80% , 90% ? Still think that you' re holding at full draw ? Better do some math , you' re probably holding no more than 6-8 lbs . The " hold at full draw" argument is pure crap . Try increasing the weight of your compound too , my crossbow with quiver weighs over 6 lbs , most of that forward of center .

Misinformation like that is why crossbows get no respect , try one for yourself and make your own judgement . Most of the folks who hate crossbows have never even fired one at a target , so what the hell do they know anyway ?