It sounds like the 2nd ISP is offering you a bundled ADSL service which is indeed a lot cheaper than your existing leased line.
In my experience however (I work for an ISP), most business requirements are such that they need as much download capacity as upload capacity. And, as such, a lot of companies are now utilising SDSL (where available). SDSL is not readily available whilst ADSL generally is.
However the reduced upload capacity of ADSL may not be an issue for you depending how much traffic you anticipate will leave your network. You say you have people doing remote support. Does this mean they simply carry out remote access (low bandwidth requirement) or are they more likely to be moving files around and uploading them to remote servers (high upload requirement).
My advise would be to try and better understand your business processes regarding your Internet utilsation. If you deem it likely you will be pushing a lot of traffic out of your network, consider staying with Leased Line or moving to SDSL (if available). If you feel that generally a lot of traffic is not leaving your network then business ADSL could be a better option.
ALterntively if you're really not sure how your business is using your Internet connection, you could try calling your current ISP and request a historical utilisation graph of your connection. Most ISP's utilise something like MRTG or Concord etc that pretty much tells them how heavily utilised any particular WAN service is.
HTH