I won't make the same point here once again about how subjective the term "Best" can be as I believe other's have already made that same point better than I could.
However: I will assume by the term "Best" you mean a reliable software with a good developer who cares about the userbase and provides a reliable undetected bypass for very long periods of time.
(Actual Private) Tuski: This software is genuinely private. Invite only, low user-base, large feature list. Do not DM me inquiring about an invite, I suggest doing some research and getting to know people in software using communities.
(Slotted) Cxmplex Software: Cxmplex is an outstanding Dev and provides some wonderful support and software alike. Fair warning however, his software is *actually* slotted and you could very well be waiting months for a response as he will typically only respond when a slot is actually open as opposed to having his time wasted or wasting yours. Great Dev, highly recommend.
(Hardware AKA - *DMA*) In terms of remaining unbanned, hardware software such as what's made around a DMA card is some of the best you can achieve safety wise. DMA cards are expensive, require two PC's and a decent internet connection. However, they remain some of the safest options on the market in terms of remaining unbanned. I would recommend AtomicDMA for DMA related software on Tarkov.
Those are three top-tier software's available on the Market for Tarkov. I do not and would not recommend subpar quality software or software I would personally not use myself.