If you decide to go with propane/MAPP over butane and really want power, good combustion, and ease of use, get a Bernzomatic TS8000 or the BZ8250HT for $49 and $69, respectively. The 8250 has the torch on a 5 foot hose, so you don't have to lug the whole bottle around when searing. I think that's ideal for line work. They both have a swirling nozzle that makes for complete combustion and they dump HUGE amounts of heat (>14k BTU/hour w/ propane), so you can get toasting quickly. My favorite feature is that they have the crispest "instant on" triggers of any torch I've used: even with a quick pull of the trigger for a fraction of a second, it's very responsive. I found them cheapest at Home Depot AND you get a free tank of MAP-Pro. You'll get about 1.5-2 hours continuous use out of one tank.
As for propane vs MAP-Pro (true MAPP isn't available anymore, Linde stopped making it in 2008), the jury is out. MAP-Pro only gets 130 ˚F (a measly ~3%!!!) hotter in air: it's only appreciably hotter than propane when you mix it with pure oxygen (~5200 ˚F vs 4500 ˚F). Modernist Cuisine says "We strongly prefer torches fueled by MAPP or propylene gas" without much discussion, but Chris Young (one of the authors that later left the project before MCAH) says propane is really just as good with a good/properly adjusted torch. The way I see it, the key is that if a torch is MAPP-compatible, it usually indicates that it is better made and gives more complete combustion, even with propane, and MC wanted to KISS for editorial reasons.
http://forum.chefsteps.com/discussion/13/mapp-gas-vs-propane-torches
http://modernistcuisine.com/2011/02/torch-tastes/
I use propane with a properly adjusted flame and have no problems. Gotta occasionally twirl the torch tip to adjust the air/fuel mix until there's no yellow in the flame before pointing it at food, and you're good to go. MAP-Pro is too expensive compared to any perceived benefit for me, though I suppose if you look at the actual cost of searing (~10¢/minute with MAP-Pro versus ~3¢/minute with propane), the difference may not matter to you. For me, burning MAP-Pro is about the same cost as paying minimum wage, haha (albeit very part-time), so I go propane.
And it's still the case that radiant heat causes less off flavor than direct flame, so the chinois trick is still pretty useful, even though it's necessarily a bit slower.
Pardon the rant. This is a topic I have spent tooooo much time thinking about and figured I'd pass along my take.