hi forex,
Obviously MD can only present the data as it is supplied. There are alot of idiosyncracies with the way data is provided by the various exchanges/platforms and then how it is processed and supplied by data vendors.
It's just no practicable to expect to receive actual trade-by-trade data for a bunch of markets across the globe, real-time with no apparent latency even during fast-markets, across an internet connection to some form of wintel based app running god knows what else, all for $80 per month. This is especially the case with the dramatic increases in futures markets/volume in recent years.
Institutional-grade solutions are available but well beyond the reach of we mere mortals.
Having said that the data aggregation being undertaken by the CME, IB, eSignal etc etc means that we get access to timely data at a very reasonable cost, at the expense of some granularity. A worthwhile compromise from my perspective. I don't wish to sound like an exchange/ data vendor apologist - by I am a pragmatist. And anybody who has traded for 5 or 10 years will know how far trading technology has come in that time.
Having said all that, the big vs small delta works fine on CME data. It's obviously not 100% accurate but thats not important. It's a broad concept at best and as such does not engender itself to finely-tuned measurement. It definitely provides an advantage - so I am happy to use it in it's current form.
Good luck,
bolter