Following is a comparison of the two major depreciation proposals put before the Senate Finance Committee, the 10-5-3 plan advocated by Republicans and the 2-4-7-10 plan introduced by Sen. Lloyd Bentsen (D-Texas) and approved by the committee with amendments. In General 2-4-7-10 Has no phase-in peroid. It would establish four categories of write-off periods for personal property, based loosely on the current useful life categories now used, with another category for buildings. It would switch to open-ended accounting, whereby firms put all investment into one of the four categories, regardless of when acquired. There now are "vintage accounts" with separate accounts for investments acquired in different years. By an amendment approved yesterday, the rules were labelized to allow both depreciation and investment tax credits (ITC's) to be claimed while the assets are being built, if they take at least two years to build. 10-5-3 Would phase in over five years and would put depreciable business property into three categories: cars and trucks, machines and equipment, and buildings. Machines and Equipment 2-4-7-10 Business property that now is considered to have a useful life of up to 6 1/2 years (such as trucks, special tools and oil and gas drilling equipment) would be depreciated over two years and could get a 2 1/2 percent ITC. Property now with useful lives of between 6 1/2 and 11 1/2 years (such as mining equipment, electronic manufacturing, wholesale and retail trade) would be written off in four years and could claim a 6 percent ITC. About half the auto industry's investment in tools, now written off in three years, would go here. Property now with average useful lives of between 11 1/2 and 16 1/2 years (such as primary steel products or car manufacturing assets) would get written off over seven years with the full 10 percent ITC. Property with useful lives now of more than 16 1/2 years (such as cement or sugar manufacturing) would be written off over 10 years. Public utility property would remain under the current Asset Depreciation Range system, but it could be written off 30 percent faster or slower than the useful life assigned to it (currently the range is 20 percent). 10-5-3 Up to $100,000 in cars and trucks could be written off over three years and would be eligible for a 6 percent ITC. Business machines and equipment could be written off over five years and could get the full 10 percent ITC. Includes an unlimited carryover to future years of unused depreciation deductions. Real Estate 2-4-7-10 Industrial, commercial adn residential real estate could be depreciated over 20 years using a straight line method. Is elective. Owner-occupied business buildings, such as Mom-and-Pop stores, could be depreciated over 15 years, by an amendment approved yesterday. 10-5-3 Industrial and commercial real estate (but not residential, such as apartment houses) would be depreciated over 10 years, with larger write-offs in the early years. Not elective. Cost 2-4-7-10 Before the amendments approved yesterday, estimated to start at $4.7 billion in fiscal 1981, rising to $18.4 billion by fiscal 1983 and declining to $18 billion in 1985. 10-5-3 If phased in, would start at $2.4 billion in fiscal 1981 and rise to $48 billion in fiscal 1985. Fully effective, would start at $4.7 billion and rise to $61.2 billion in fiscal 1985.