If money is tight, you will save my buying direct. But you do have to check with EPA, and use a customs clearance agent. If you can save on shipping, even better. The down side is, any problems and you have to talk direct to India. This is not easy and there is no guarentee any spares you get will be the same spec as what went into your engine. Warranty is best forgotten about to be perfectly honest about it. Getting spares is as good as it gets, and those will take 4 to 5 weeks to reach you....then they go through customs etc.
You should tear down the engine if you buy direct, this is more or less a prerequisite.
If you buy locally, yes you do pay more, but at least you have a native english speaking person to deal with, and your problems should be resolved much faster i.e little down time. Most people do not want the hassle of having try and get the spares themselves and wait for the slow boat from India.
You could also keep an eye on ebay for old genuine Lister engines. Most need repair, but they are a proven design and putting money into one carries definate payback.
Pro's and Con's to each way you look at it. What ever you feel more confortable with, I would let that decide rather than just the money aspect alone.
Rdgs,
Emerald