Seems to me it's pretty much swings and roundabouts. I haven't yet found an app that does everything I'd like. I've been using the Aviva Expert which is a smart meter and really like it for the bolus and correction advice, but the screen is too small for the graphs to be much use, apart from the numeric averages. I use that a lot. I haven't get bought the cd to transfer data to my PC. I've been using the Expert in tandem with MyFitnessPal for carb counting and I utterly depend on that. Brilliant app and it's free.
A few days ago I splashed out £5.99 for RapidCalc, which gives bolus advice and the graphs look good. But obv its not a meter as well. It only runs on one device with no built in syncing which is a pain. I'd hoped to have the bigger screen of the iPad for the graphs and the portability of the iPod. I'm certainly not entering the stuff twice. So far I've discovered it won't let me enter bolus doses without doing a BG test but I can enter historic data if I've done the BG test first. Apart from that it looks as if it will be good.
I just checked out Diabetes Connect. The graphs look good and you can input historic data, which I like. But no bolus advice.
For me the big must have is the bolus advice. I'm relatively new to that and think it's brilliant. What I'd like is a smart meter with the onboard software of RapidCalc. The Expert and RapidCalc both keep track of IOB so I avoid insulin stacking and the resultant hypo. Maybe I'm too picky but everything I'd like doesn't seem to come in one package. But, oh how things have changed from when I was diagnosed. It seems churlish to be griping about the shortcomings of apps!
Nearly forgot. I tried Mysugr too and gave up after a few minutes. The chatty style and cartoons just drove me bonkers.