well I started out open diff and it didnt really take me that long to figure out how to drift both directions. there were only 2 mods to my car bigger front tires and an exedy stage one clutch and i got that simply cause it was cheaper than a stock replacement ($230 vs. $450) and i had to work around a 3000 lb car with open diff, 60/40 weight disp, almost blown stock susp, 18 year old bushings and only 160hp at the crank (probly less) . I basically had the crappiest car at the events
It may take a while to get good with a bad setup but in the end i think it makes you more adaptable to other setups. as far as welding well if your ever up in orlando bring my dad and I an extra diff and we'll weld it for you for free. My dad has 15 years of welding expience the only metal he hasent welded on yet is titanium and he can Mig Tig Arc and Gas. At one of the places he worked in michigan had him welding together inconel headers for old military tanks.
What my dad says would be the ideal way to weld a diff is to put it in an oven and heat it slowly up to 600* and let it bake for 2 hours in the oven then pull it out and weld it around the side gears and then put it back in the oven and take the temp down very slowly over another 2 hr period. He says after that you will have a diff that aint never gonna break.