Copper sweat fittings

[daysaver1]

I've completed the stainless economizer which will live in the smoke box of my Semple VFT boiler and am gathering parts to connect it to my feed water supply. I'm planning to use "L" strength copper tubing for supply line but between the end flare couplings I need to install a couple elbows which I'll silver solder to the "L" copper. My question is if anyone can give me a comparison of strength between standard copper elbows used by most plumbers and the cast copper alloy elbows which look much stronger. I have a good supply of both.