Spreadbetting through a UK-registered SB firm is fine, as long as you don't misuse the account. What I mean is its not the best approach for very tight very short-term intra-day trading, what some people call scalping, the spreads are too wide. The range of markets is also limited, for example I reckon the firm I use only offers about a quarter of the AIM 100. For other stuff, its a good tool.
The decision as to whether to CFD or whether to SB will not affect whether your win or lose.