I did not mean to come across as being emotional but what you said is simply wrong. Most CFDs trade at a bid-offer spread. Most also charge commission, they charge interest on a daily basis. So yes, while the initial quote in some CFDs (only DMA single stock CFDs) might be identical with the underlying nothing at all is identical when it comes to the pricing of the whole contract. You can't say just because the initial quote is identical that the pricing is identical, completely ignoring the ensuing cash flows such as interest charges. For all non DMA or non single stock CFDs even the initial quotes are not identical with the underlying for obvious reasons. Also consider that some non DMA brokers re-quote and even IB as DMA CFDs intermediary may delay execution for various reason and hence get you a worse price (at least a different price than anticipated).
And no, it is NOT the exact same as trading the underlying, how can it be if the economic benefit is different? I do not understand your rational or maybe definition but clearly the two are not identical else you would not trade the CFD in the first place. The economic costs/benefits are NOT identical even for DMA exchange traded CFDs (interest charges alone and completely different financing structures demolish the equality ). Additionally, non-customary dividend payment structures or corporate actions in the underlying can sometimes not be replicated by the CFD.