All the girls love me 'cause I got LEGITIMATE hardware, baby...
Personal choice, both options work fine, but I prefer the hardware route.
Check for machines by a company called ZOOM.
RhythmTrak RT-123
or
RhythmTrak RT-323
or, if you wanna get into sampling drum sounds and so forth to accentuate your SR-16, check this out...
Zoom Sampletrak ST-224
http://www.zoom.co.jp/english/englishie_index.html
Also, check out the Boss Dr. Groove DR-202
http://www.bossus.com/index.asp?pg=1&tmp=53
I'm sure there are others that peoples around here can recommend or encourage you to stay away from.
I can't really call it & say 1 method of working is easier or better than others, i'll leave that to the Master Debators, I can only tell you that as much software as I use for shit, I
still prefer the hardware any day of the week.
When you say how much you got to spend (and if you're computer is able to handle soft-drum-synths), maybe you'll get some more budget-appropriate suggestions.
1. Are you willing/able to buy used (like from Ebay)?
2. What are the specs on your PC?
3. What other equipment or software do you have/are you planning to buy?
4. Have you checked the equipment-for-sale forum here?
All those things (and probably others) can make a difference (to some degree) in the information people offer up.

What the fuck do I know, though?
I'm just a damn DJ...
Good luck.
Diendolo